MaxApki: MnożenieMax, StoliceMax, ChemiaMax, LiteraturaMax, JęzykiMax, MapkiMax, AstronomiaMax and BiologiaMax

A prototype browser app that teaches the multiplication tables with flash cards. The cards are scheduled with FSRS, the algorithm Anki offers alongside its older SM-2.

The same page also holds seven sister apps with the same options: StoliceMax, which teaches the capitals of countries, ChemiaMax, which teaches the formulas of elements and common chemical compounds, LiteraturaMax, which teaches who wrote well-known books, JęzykiMax, which teaches French, Spanish, Dutch, Italian and Polish, MapkiMax, which teaches where cities, mountains, lakes, rivers, seas, islands and deserts are on the map, AstronomiaMax, which teaches facts about the Solar System, stars and spaceflight, and BiologiaMax, which teaches facts about animals, plants, the human body and evolution. The eight apps form a family, MaxApki, installed as one app at one address. Tapping the app name at the top of the screen opens a menu with all eight.

Running it

The app is published with GitHub Pages at https://maxapki.top/, from the repository gchrupala/maxapki. Until every tablet has moved there, the earlier address, https://grzegorz.chrupala.me/Anki/, is served from gchrupala/Anki (see Moving to maxapki.top).

Open index.html in a browser. There is no build step and no server is needed.

Run the scheduler tests with Node 18 or later:

npm test

Installing on a tablet

The app can be installed as a home-screen app (a "progressive web app"). It then opens full screen, without the browser bars, and works without internet after the first visit.

This needs the files on an https web address, for example GitHub Pages (repository Settings → Pages → Deploy from a branch → main, / (root)). The empty .nojekyll file tells GitHub Pages to publish the files as they are, without its Jekyll site generator. GitHub Pages for a private repository needs a paid GitHub plan; Netlify and Cloudflare Pages can serve a private repository for free.

Then, on the tablet:

• iPad: open the address in Safari, tap the Share button, then "Add to Home Screen".
• Android: open the address in Chrome, open the ⋮ menu, then "Install app" or "Add to Home screen".

The home-screen name is "MaxApki.top", and its icon shows the cards of the eight apps on a deep blue background. (The app installed from the old address is called "MaxApki", and its icon has a rainbow background.) MnożenieMax, StoliceMax, ChemiaMax, LiteraturaMax, JęzykiMax, MapkiMax, AstronomiaMax and BiologiaMax are opened from inside it. On a tablet where the app was installed as "MnożenieMax", Chrome updates the name and icon by itself when it next checks the app, which can take up to a day; it may ask to confirm the change. Progress is stored on the tablet only, separately from the browser, and is lost if the app is removed. To keep it, or to move it to another device, save it to a file first (see Moving progress) or back it up on GitHub (see Backing up to GitHub).

The offline copy is kept by sw.js (a service worker). On every launch it asks the server whether the app files have changed, so a pushed change appears the next time the app is opened online, once GitHub Pages has published it (usually within a minute or two). Without internet, or if the server takes more than 4 seconds to answer, it uses the stored copy. A change to sw.js itself takes one extra launch: the first launch installs the new sw.js, the second uses it. Opening index.html as a local file still works, but without the offline copy or installation.

Languages

The interface follows the device language when it is Polish, English, Dutch, Spanish or Persian, and is in Polish otherwise. A fixed language can be chosen in the settings panel ("Ustawienia", behind the gear button); the first entry in the menu goes back to the device language. All languages write multiplication with ×. Persian is shown right to left, with Persian digits (۷ × ۸ = ۵۶); sums, the keypad and the progress square stay left to right, as in Persian maths. A keyboard may type Persian, Arabic or Western digits. All text is in i18n.js, and the text that differs in StoliceMax in i18n-capitals.js. Times such as "tomorrow" or "in 3 days" and plural forms come from the browser (Intl.RelativeTimeFormat and Intl.PluralRules).

How it works

Each fact, such as 7 × 8, is one card. 3 × 7 and 7 × 3 are separate cards. The tables go up to 12 × 12 (or 10 × 10). On top of that, extra numbers can be chosen, by default 15, 20 and 25. Each extra number is practised only with the numbers 1 to 12: there is 15 × 7 and 7 × 15, but no 12 × 14 and no 15 × 20. With the defaults that makes 216 cards (144 + 3 × 24).

The child types the answer on the on-screen keypad or the keyboard. The answer is checked as soon as it has as many digits as the right answer. A shorter answer is checked after 3 seconds without typing, or when the child presses OK. If nothing is typed within the time limit (10 seconds by default; 10 to 60 seconds or no limit in the settings), the fact counts as not known: the app shows the answer, as after a wrong answer. The limit pauses while the settings panel is open or the app is in the background. The app then picks one of the four Anki ratings on the child's behalf:

Answer	Anki rating
Wrong, or nothing typed within the time limit	Again
Right, but slower than 10 seconds	Hard
Right	Good
Right within 4 seconds	Easy

Easy is only given when the card is shown for the first time or as a review. During the short learning steps the child saw the card a few minutes earlier, so a quick answer then says little about long-term memory.

After a wrong answer the app shows the right one, and the child types it to continue.

After a right answer the card stays on the screen for 1.4 seconds (2.2 when coins are paid), then the next one comes by itself; after a wrong answer, once the right one is tapped, it stays 0.9 seconds. A "Zatrzymaj" (Wait) button under the card shows the time left as a shrinking line. Tapping it keeps the card on the screen to look at it; the button then reads "Dalej" (Next), and tapping it, an answer or a key moves on. Tapping the card before it is held moves on at once. The setting "Następna karta po" (Next card after) keeps these times by default ("1,4 s"; in JęzykiMax the default is 5 seconds), or sets the time to 2, 5 or 10 seconds, or to "natychmiast" (at once: the next card comes after 0.4 seconds, just long enough to see the answer turn green, with no time for the coin message or a translation), or keeps every card until "Dalej" is tapped. Each app has its own setting.

Once a card has been answered, a "Cofnij" (Back) button in the head of the card goes back to the card answered last. Its answer is taken back: the card, the review log, the counts of the day and the coins the answer paid are as they were before it. The card is then asked again, with the same answers to choose from. Each tap goes one card further back, through the answers given since the app was opened; Ctrl+Z (⌘Z on a Mac) does the same, as in Anki. It cannot go back to an answer given on another day, before a switch to another app or (in JęzykiMax) another language, or before the progress was erased, nor to an answer whose coins have been spent in the shop. The bonus for finishing the day is kept. On a narrow screen the head of the card takes two lines when the button does not fit next to the rest.

Scheduling

srs.js implements FSRS-6 with its default parameters, following the reference implementation py-fsrs.

• FSRS keeps two numbers per card. Stability is the number of days until the chance of remembering drops to 90%. Difficulty runs from 1 to 10 and controls how fast stability grows.
• The next review is set for when the chance of remembering is expected to fall to the target recall: 90% by default, adjustable from 80% to 95%.
• New cards go through learning steps of 1 and 10 minutes before their first interval in days. A forgotten card goes through a 10-minute relearning step.
• Intervals get a small random shift ("fuzz"), as in Anki, so cards learned together don't keep coming back together.
• As in Anki, a day starts at 4 am and elapsed time is counted in calendar days. When only learning cards are left, they are shown up to 20 minutes early.

Coins

Coins reward what the child remembers, not the number of cards done. In spaced repetition a well-known fact comes back rarely, so coins per answer would reward forgetting. Instead:

When	Coins
A new fact is learned (it leaves the first-day steps)	2
The gap before its next review reaches a week	5
The fact is mastered (a gap of 21 days or more)	10
All of the day's cards are done (once a day)	10

Each fact pays each reward once, so forgetting and relearning earns nothing. Coins never change the schedule. Facts learned before coins were added counted towards the starting balance.

Coins are spent in the shop ("Sklep" in the header) on rewards of the child's choice. In MnożenieMax these are keychains with the prime numbers from 2 to 19, each hanging from a key ring on a short chain. Prices rise with the number and its material:

Keychain	Coins
Bronze 2	50
Silver 3	100
Gold 5	150
Platinum 7	250
Diamond 11	350
Ruby 13	500
Emerald 17	650
Sapphire 19	800

Until October 2026 these were trophies in the same materials. A trophy bought then now shows as the keychain of its material.

Buying takes two taps (buy, then confirm), so a mis-tap does not spend coins. A purchase shows the keychain and lets confetti fall from the top of the screen for 4 seconds; with reduced motion switched on in the device settings, only the keychain is shown. The coin counter in the header shows the coins that can still be spent; next to it is the button of the collection, with the number of rewards in all the apps and the latest one bought in this app. The shop lists all keychains bought, with their number next to the heading of the list. A keychain for sale that is already in the collection is marked with how many there are, such as ×2. The settings show the coins collected and spent. Tapping a reward on that list, or in the collection, shows it large, glowing in its colour, with its name and the date it was bought; a keychain swings gently on its ring. This works the same in all the apps. Done, Back or a tap around it goes back to where it was opened from. Prices, numbers and materials are set in TROPHIES in index.html (the code still calls all rewards trophies), the rewards in LEVEL_COINS and DAY_BONUS. In a simulation of a child practising daily with 10 new facts a day, buying each keychain as soon as possible, the bronze 2 comes on day 1, the gold 5 on day 5, the diamond 11 on day 13 and the sapphire 19 on day 29.

Order of cards

• At most 10 new facts are introduced per day (adjustable). They are picked in a random order from all the selected tables, so easy facts such as 1 × 4 and harder ones such as 7 × 8 are mixed from the first day. To focus on particular tables, switch the others off in the settings panel.
• Cards that are due in their learning steps come first. Otherwise the next card is drawn at random from today's reviews and new cards.
• The card just answered and its twin (7 × 3 after 3 × 7) are not shown next unless nothing else is left.

Settings and review log

The settings panel (the gear button, "Ustawienia" in Polish) lets you:

• choose the language;

• choose the size of the table (10 × 10 or 12 × 12), which tables to practise and which extra numbers to add (13 to 20, and 25);

• change the number of new facts per day and the target recall;

• switch the sound of the fireworks on or off (StoliceMax only; on by default);

• move the app clock ahead by a day, to see how reviews come back;

• save the progress of all the apps to a file, or load such a file (see Moving progress);

• copy the review log as CSV.

The explanations in the panel (what a setting does, how the cards are scheduled, how coins are earned, how to move progress) are folded. The "i" button next to a setting or a heading shows or hides them.

The log has one row per answer. Its first five columns (card_id, review_time, review_rating, review_state, review_duration) are the input format of the FSRS optimizer, so the log can be used to fit FSRS parameters to one child once there are enough reviews. Two more columns give the fact and the typed answer.

The progress square shows each fact: not started, practising (in the learning steps), learned, or mastered (interval of 21 days or more, which Anki calls "mature").

StoliceMax

StoliceMax teaches the capitals of countries. It runs in the same page and at the same address as MnożenieMax, and has the same options: scheduling, time limit, coins and shop, languages, settings, review log, updates and offline use.

Switching apps

The app name at the top of the screen is a button. It shows the icons of the apps and an arrow, and opens a menu with all the apps. Inside the app each icon has the colour of its app, with a card and a drawing in black and white; the home-screen icon of MaxApki is in full colour. For each app the menu says what it teaches and how many cards it has left today; an app not opened yet is marked "nowa" (new). The menu opens by itself the first time, and again the first time after a new app was added, and then explains how many apps there are. When all of the day's cards are done, the done card has a button to another app that still has cards for today.

The app that was open last opens on the next start. The address can also name the app: #mnozenie, #stolice, #chemia, #literatura, #jezyki, #mapki, #astronomia or #biologia at the end (https://maxapki.top/#stolice). For a short time StoliceMax had its own address, https://grzegorz.chrupala.me/Anki/stolice/ (now also https://maxapki.top/stolice/). That address now leads to #stolice, and its offline copy removes itself.

The share button in the header (three connected dots) opens the share menu of the device with the address of the app, https://maxapki.top/, for example to send it in a message. Where the browser has no share menu, it copies the address and says so.

Each app keeps its own cards, coins and rewards. The coins of MnożenieMax have an embossed ×, those of StoliceMax a star, those of ChemiaMax an atom, those of LiteraturaMax an open book, those of JęzykiMax a speech bubble, those of MapkiMax a compass rose, those of AstronomiaMax a planet with a ring, those of BiologiaMax a butterfly. The atom is also the symbol on the ChemiaMax card in the app menu; the home-screen icon of MaxApki still shows a flask. The language is shared.

Cards

• Each country is one card: the 193 members of the United Nations and the Vatican. The card shows the flag and the name of the country, and the child picks the capital from four capitals of the same continent, shown in a random order. After a wrong answer, or when the time is up, the right capital turns green and the child taps it to continue.
• The ratings follow the table above, with two differences. A right answer the first time a country is shown is never Easy, because with four answers it may be a guess; the country goes through the learning steps. Easy needs a right answer within 5 seconds instead of 4, because reading four names takes longer than typing a number. The default time limit is 15 seconds.
• The settings choose the continents; Europe is on by default. The continents follow Polish schools: Russia and Cyprus are in Europe, Turkey in Asia, and North America includes Central America and the Caribbean.
• The progress view has a square with the flag of each country, grouped by continent, with the number of capitals learned on each continent. A flag shows in colour once its country has been answered.
• The review log has a column for the country and one for the country whose capital was picked, both as ISO codes. The card_id the FSRS optimizer needs is the ISO code with its letters as numbers (FR is 618).

Rewards

Coins follow the same rules as in MnożenieMax (2, 5 and 10 per country, 10 per finished day). The shop sells souvenirs: keychains with small glittering models of famous sights in capitals, hanging from a key ring on a short chain.

Souvenir	Capital	Coins
Palace of Culture and Science	Warsaw	50
Eiffel Tower	Paris	75
Canal houses	Amsterdam	100
Big Ben	London	125
Giant Ferris Wheel	Vienna	150
The Bear and the Strawberry Tree	Madrid	175
Brandenburg Gate	Berlin	200
Yellow tram	Lisbon	250
Atomium	Brussels	300
Colosseum	Rome	350
Parthenon	Athens	400
White House	Washington	450
Torii gate	Tokyo	500
Azadi Tower	Tehran	525
Petronas Towers	Kuala Lumpur	550
Lotus Temple	New Delhi	600
Cathedral of Brasília	Brasília	650
Sheikh Zayed Mosque	Abu Dhabi	700
Pyramids of Giza	Cairo (Giza is part of greater Cairo)	750
Forbidden City	Beijing	800

All 20 together cost 7700 coins. Learning all 194 capitals to the mastered level pays 3298 coins, and each finished day adds 10, so the full collection is a long-term goal. Each souvenir glitters: two layers of tiny coloured dots shimmer in turn, three stars twinkle on it, and a beam of light passes over it now and then. In the header the glitter stays still, so it does not distract from the cards. Buying a souvenir shows fireworks for 4 seconds: the screen darkens and rockets rise from the bottom and burst into sparks. A quiet sound goes with them: a whistle and a hiss as each rocket rises, and a bang with a crackle as it bursts, from the side of the screen where it is. The browser makes the sounds itself (Web Audio), so there are no sound files. The sound can be switched off in the settings ("Dźwięk fajerwerków"). Keychains in MnożenieMax keep their confetti. With reduced motion switched on in the device settings, the glitter stands still and only the souvenir is shown when one is bought.

The souvenirs and their prices are set in SOUVENIRS in index.html, their drawings, the places of their stars and the point where the chain holds them in SOUVENIR_ART, and their names in i18n-capitals.js.

Names of countries and capitals

The names are in countries.js. Country names come from the Unicode CLDR data that browsers use for Intl.DisplayNames, capitals and their names from Wikidata. Both were checked and some were corrected by hand. Some choices to be aware of:

• Where a country has more than one capital, the app uses the one Wikidata lists first: Pretoria (South Africa), Sucre (Bolivia), Porto-Novo (Benin), Yamoussoukro (Côte d’Ivoire), Dodoma (Tanzania), Gitega (Burundi), Mbabane (Eswatini) and Sri Jayawardenepura Kotte (Sri Lanka). The others never appear as answers.
• Equatorial Guinea has Ciudad de la Paz, which replaced Malabo in January 2026 according to Wikidata. Older school books give Malabo.
• Israel has Jerusalem, as in Wikidata. Many countries do not recognise it as the capital.

ChemiaMax

ChemiaMax teaches the formulas of elements and common chemical compounds. It runs in the same page as the other apps and has the same options.

• Each card is an element or a compound: 28 elements and 53 compounds a child meets at home, in nature and in school chemistry, from oxygen, iron and gold to water, table salt, caffeine and vitamin C. Elements are written as they occur: gases such as oxygen as molecules (O₂, N₂, Cl₂), noble gases and metals as single atoms (He, Fe, Au), and sulfur, carbon and phosphorus by their symbol. The card shows the name, as in school chemistry ("Tlenek węgla(IV)" in Polish), with the everyday name below it if there is one ("dwutlenek węgla"). The child picks the formula from four, written with small numbers (H₂O).
• One wrong answer is always the formula most like the right one, and two more come from the next five most like it. For a compound, alike means the most of its elements and the fewest others: carbon monoxide always gets CO₂, and nitrogen dioxide N₂O and maybe HNO₃. For an element, it means another form of the same element or a symbol with the same first letter: oxygen always gets O₃, iron F₂, silver Au, Ar or Al.
• As in StoliceMax, a right answer the first time is never Easy. Easy needs a right answer within 6 seconds. The default time limit is 20 seconds, and 5 new compounds a day, because formulas are harder to learn than capitals.
• The settings choose the groups: elements, oxides, acids, bases, salts and organic compounds. All are on by default; the elements, added later, were switched on for progress saved before them. The progress view has a square with each formula, by group. Since the square shows the answer, the card being asked is only marked on it once it has been answered, and the label that shows when the mouse is over a square gives only when it comes back, not the name of the compound.
• The review log uses the number of the element or compound in chemistry.js as card_id, and has the formula and the formula picked.

The shop sells laboratory glassware with coloured liquid that bubbles and glitters:

Glassware	Coins
Blue test tube	30
Green test tube	50
Pink conical flask	70
Purple retort	100
Orange round flask	140
Rack of test tubes	175
Yellow beaker	200
Retort over a flame	275
Turquoise volumetric flask	350
Separating funnel	425
Golden retort	500
Rainbow flask	575

The prices are about a third lower than in the other shops, since ChemiaMax has fewer cards to earn coins with. Buying one makes an elixir explode, for 4 seconds in all: a bottle of glowing green elixir appears, shakes harder and harder while it bubbles, and its cork pops off. Then it bursts with a green flash and a shock wave, glass shards and green droplets fly all around, some splash onto the screen and drip down, green mist rises with sparkles in it, and the page shakes. With reduced motion switched on in the device settings, only the glassware is shown. The glassware and its prices are set in GLASSWARE in index.html, the drawings in GLASS_ART, the names in i18n-chemistry.js.

The elements and compounds and their names in the five languages are in chemistry.js. No two share a formula; glucose is there, fructose (also C₆H₁₂O₆) is not. Some everyday names stand for a close relative: gypsum is CaSO₄ with water in it, and the Persian کات کبود is copper sulfate with water.

LiteraturaMax

LiteraturaMax teaches who wrote well-known books. It runs in the same page as the other apps and has the same options.

• Each card is a book: 126 books by 125 authors from 39 countries, in 26 languages, in seven categories: children's books, books for young people, fantasy and science fiction, crime and detective stories, adventure, classics, and poetry and epics. Eastern Europe and the Middle East are well represented: there are books from Poland, Ukraine, Russia, Czechia, Hungary, Bulgaria and Georgia, and from Iran, Egypt, Lebanon, Turkey and Morocco. There are also books from South Asia (India and Pakistan), East Asia (China, Japan and Korea), Latin America (Argentina, Uruguay and Brazil, besides Colombia) and Africa (Nigeria, Senegal and Kenya), and Dutch children's books.
• The card shows the title in the language of the page where the book has a well-known title in it, and below it the original title and the language the book was written in, such as "Крокодил Гена и его друзья · język rosyjski". Language names come from the browser (Intl.DisplayNames). Without a title in the language of the page, the card shows the original title if it is in the Latin alphabet, or else the English title.
• The child picks the author from four. One wrong answer is always the author most like the right one, and two more come from the next five most like it. Alike means writing in the same language (3 points), coming from the same country (2) or writing in the same category (2), so a Persian poem gets other Persian poets and a Polish adventure book other Polish authors. Each author appears once among the answers.
• As in StoliceMax, a right answer the first time is never Easy. Easy needs a right answer within 6 seconds. The default time limit is 20 seconds, and 5 new books a day. All categories are on by default.
• The progress view has a square for each book, with the flag of the country of its author, by category. As in ChemiaMax, the book being asked is only marked once it has been answered, and the label over a square leaves out the title, since the flag hints at the author.
• The review log uses the number of the book in literature.js as card_id, and has the book and the book whose author was picked (as b1, b2 and so on).

The shop sells literary prizes from many countries and international ones, each a glittering medal on a ribbon or a statuette. Four white stars with a soft glow twinkle on each prize, besides the small golden ones the souvenirs have:

Prize	Country	Coins
Newbery Medal	United States	30
Carnegie Medal	United Kingdom	40
Franz Kafka Prize	Czechia	50
Prix Goncourt	France	75
Cervantes Prize	Spain	100
Shevchenko Prize	Ukraine	125
Jalal Al-e Ahmad Prize	Iran	150
Gouden Griffel	Netherlands	175
Hugo Award	international	200
International Prize for Arabic Fiction	international	250
Nike Award	Poland	300
Booker Prize	United Kingdom	375
Hans Christian Andersen Award	international	450
Nobel Prize in Literature	Sweden	700

All 14 together cost 3020 coins; learning all 126 books to the mastered level pays 2142, plus 10 for each finished day. The Nobel medal is the largest and has golden rays around it. Buying a prize sets off a rain of letters: letters of the Latin, Cyrillic, Greek, Hebrew, Arabic and Persian, Georgian, Armenian, Devanagari, Thai, Chinese, Japanese and Korean scripts fall and turn. Each letter lands at the bottom of the screen and only fades there; new letters come for just over 2 seconds, and the last ones have faded about 5 seconds after the purchase. With reduced motion switched on in the device settings, only the prize is shown. The prizes and their prices are set in PRIZES in index.html, the drawings and the places of the white stars in PRIZE_ART, the names in i18n-literature.js.

The books and authors and their names in the five languages are in literature.js. Titles were chosen from published translations where they are well known; where a book has no known title in a language, the field is left empty and the rule above applies.

JęzykiMax

JęzykiMax teaches French, Spanish, Dutch, Italian and Polish at the levels A1, A2, B1 and B2 of the Common European Framework of Reference for Languages. It runs in the same page as the other apps and has the same options. The language to learn is separate from the language of the interface: five buttons above the card choose it, and each language has its own cards and its own number of new cards a day. The coins of the five languages go into one purse.

• The cards are only in the language being learned, with pictures (emoji). The instruction ("Co to jest?", "Which word is missing?") is in the interface language. There are five kinds of card, each with four answers:
  • a picture, and the child picks the word or phrase ("la pomme", "Il pleut.", "Tengo frío.");
  • a word or phrase, and the child picks the picture;
  • a sentence with a gap, and the child picks the missing word ("Je vais ___ école." with "à l’", "au", "à la", "aux");
  • a question, and the child picks the answer that fits ("¿Por qué llegas tarde?" with "Porque perdí el autobús.", "Con mi hermano.", "A las nueve.", "En la cocina.");
  • a word, and the child picks its opposite.
• Each language has 750 to 800 cards: 176 pictures (vocabulary with articles, everyday phrases, idioms at B1 and B2), each as a picture card and a word card, 230 to 275 sentences with a gap, 130 to 143 questions and 36 pairs of opposites. Gaps and questions were written for each language and test its grammar: articles and gender, verb forms, past and future tenses, pronouns, at B1 the subjunctive, the conditional and relative clauses, and at B2 the passive, reported speech, conditionals about the past and linking words. Polish has no articles: its gaps test the cases, the gender of past-tense verbs, aspect and numerals instead. The B2 picture cards are idioms, with a picture of what they mean (🤐 for keeping a secret).
• The words learned from pictures should come back in sentences, so that the child practises them in use and not only as a picture puzzle. Each gap and question lists the picture concepts it uses (the word or phrase is in the sentence with the gap filled in, or in the question or its right answer, in any form). node tools/language-coverage.js shows, per language and theme, how many concepts come back on two or more other cards (node tools/language-coverage.js nl lists them one by one). In every language each picture word comes back in at least two gaps or questions: as the word to pick (De ___ vliegt het vliegtuig.), in a construction (Mijn tante werkt ___ piloot., Ik ___ het koud., Ze is piloot.), in a form (Twee ___ schilderen ons huis.) or, for the idioms, in a situation where they fit (Was de rekentoets moeilijk? – Nee hoor, dat was een eitje.). The wrong answers of a word gap share the article and form of the right one, so only the meaning decides.
• A new gap or question waits until the picture cards of the words it uses have been learned (they are past the first-day steps), so a word is met with its picture before it comes in sentences. A picture of a level that is switched off holds nothing back. And as Anki buries siblings, a new card that shares a word with a card answered today or still being learned waits for another day, so the same word is not asked twice within a few minutes.

Answers in the child's own words

Each language also has cards that the child answers by speaking or writing, with no answers to pick from, and cards for the article of a noun. They are in languages-recall.js and are built on the cards above. answer.js judges the answers.

• There are six kinds of card:
  • a picture, and the child says the word (nouns, colours and numbers, but no phrases, verbs or idioms);
  • a simple definition ("Dit dier blaft en kwispelt met zijn staart."), and the child says or writes the word;
  • a question with a short answer ("Welke kleur heeft een banaan?" – "geel"), and the child says it;
  • a sentence with a gap and the base form of the missing word ("Ik ___ (heten) Sara."), and the child writes the form that fits (gaps from above where the hint leaves one answer; the past tense also counts where the sentence allows it);
  • a word read aloud, and the child writes it (the words of the pictures below B2: one word, or a noun with its article);
  • a noun with its picture ("🍎 ___ appel"), and the child taps or says the article: le or la in French, el or la in Spanish, de or het in Dutch, il, lo or la in Italian. Polish has no articles, so its cards ask the gender of the noun: ten, ta or to. Nouns in the plural, and French and Italian nouns whose article is l’, have no such card.
• The definitions and questions are the same in every language, so each one is also the translation of the others: the card shows what it means in the language of the interface. The words of a definition never include the answer, nor another word that counts for it.

Language	Pictures	Definitions	Questions	Gaps	Dictation	Articles
French	122	57	39	67	136	90
Spanish	122	57	39	75	139	108
Dutch	122	57	39	77	141	112
Italian	122	57	39	66	140	89
Polish	122	57	39	121	136	103

• Pictures and questions are answered by voice, gaps and dictation in writing, and definitions either way. The settings "Odpowiedzi mówione" (Spoken answers), "Odpowiedzi pisane" (Written answers) and "Rodzajniki" (Articles) switch these cards on and off; all three are on by default. Spoken answers need speech recognition (see above). Without it, the spoken cards do not come, and definitions are written. Dictation needs a voice for the language on the device.
• A new card waits until the card it is built on has been learned: the picture card of its word, or the gap with four answers. It also waits for another day if that card was answered today. A question waits for the pictures of the words it uses, as gaps do.
• An answer counts with or without its article ("hond" for "de hond", "oiseau" for "l’oiseau"), and also with the wrong article, since the article cards practise that. Some cards accept other words ("de poes" for the cat, "la maîtresse" for the teacher, and in Polish the other genders of a colour). Case, a full stop at the end and œ written as oe do not count.
• A written answer that is right except for an accent, a hyphen or a space ("een" for "één") is nearly right and rated Hard. For a definition, one letter wrong, missing or extra in a word of five letters or more counts the same way. For a gap or dictation it does not, because there one letter is often the point (word, wordt). Easy needs the first letter within 6 seconds, so the speed of typing does not count. Letters with accents are under the field, for keyboards that lack them. After a wrong answer, the child writes out the right one to go on.
• A spoken answer counts if one of the recognizer's five likeliest texts contains it, compared by how it sounds, as for the answers to pick (see above). A word may be heard as two ("politie agent"), an article joined by an apostrophe counts as a word of its own ("l’oiseau"), and a longer word may be one letter off (a score of 0.85 out of 1). Digits count where the answer is a number. Anything else may be a word the recognizer misheard, so the card shows what was heard and the app listens again. Only "Nie wiem" (I don't know) or the time limit count the card as not known. After that, the child says the right answer or taps "Dalej" (Next).
• A right answer the first time can be Easy, since it is no guess.
• The progress view marks these cards 🗣️ (picture to name), 📖 (definition), 💡 (question), ✏️ (gap to write in), 👂 (dictation) and 🔤 (article). For them, the review log has the answer written, or the text heard after 🎤. Their card numbers start at 100000.
• The definitions, questions and hints were written for this app and have not been checked by a teacher. node tools/recall-test-progress.js makes a progress file to try these cards at once (see Files).

The shop sells symbols of cities where these languages are spoken, drawn as glittering models like the souvenirs of StoliceMax:

Symbol	City	Coins
Linden tree (from its coat of arms)	Tilburg	30
Arc de Triomphe	Paris	50
Mouth of Truth	Rome	60
Giralda	Seville	75
Dwarf (one of the bronze dwarfs in the streets)	Wrocław	90
Coat of arms	Amsterdam	100
Manneken Pis	Brussels	125
Leaning Tower	Pisa	140
Obelisk	Buenos Aires	150
Antwerp hand	Antwerp	175
Jet d’Eau	Geneva	200
Crane (the medieval port crane)	Gdańsk	225
Classic car	Havana	250
Gondola	Venice	275
Dom Tower	Utrecht	300
Mermaid	Warsaw	325
Château Frontenac	Quebec City	350
Angel of Independence	Mexico City	400
Notre-Dame de la Garde	Marseille	450
Wawel Dragon	Kraków	475
Cathedral dome	Florence	500
Erasmus Bridge	Rotterdam	525
Sagrada Família	Barcelona	600

All 23 together cost 5870 coins; learning all the cards of one language to the mastered level pays 17 coins a card, about 13,000 in all. Buying one makes thought bubbles (💭) pop up and rise for 4 seconds, with words such as "Bonjour !", "¡Hola!", "Goed zo!", "Evviva!" and greetings in many other languages and scripts. With reduced motion switched on in the device settings, only the symbol is shown. The symbols and their prices are set in CITIES in index.html, the drawings in CITY_ART, the names of the symbols and cities in i18n-languages.js.

The cards are in languages.js. They were written for this app; the French, Spanish, Dutch, Italian and Polish have not been checked by a teacher.

MapkiMax

MapkiMax teaches where places are: cities, peaks, mountain ranges, lakes, rivers, seas, islands and deserts on all seven continents. It runs in the same page as the other apps and has the same options.

• Each place is one card: 480 places, from Warsaw, the Tatras and the Vistula to Lake Baikal, the Sahara and Lake Vostok in Antarctica, with many in Poland, the Netherlands and Iran. The card shows the kind of place and its name. Below it is the map of the continent the place lies on, without names. The map moves with a finger or the mouse and zooms with two fingers, the mouse wheel or the + and − buttons; the button with four corners shows the whole continent again.

• The child taps the map to place a pin, can place it again, and confirms with OK (or Enter). The distance from the pin to the place gives the Anki rating:

  Distance	Anki rating
  More than 400 km, or no answer in time	Again
  Up to 400 km	Hard
  Up to 150 km	Good
  Up to 50 km	Easy

  The distance is along the surface of the Earth: to a city or peak, to the nearest edge of a lake, sea, island, desert or mountain range (0 km when the pin is inside it), and to the nearest stretch of a river. Unlike in the apps with four answers, a first answer can be Easy, since a pin close to a place is no guess. The time taken does not count, and there is no time limit by default.

• After OK the map shows the place in green with its name, and a dashed line from the pin to the nearest point of the place, and zooms to show both. After a right answer the card stays at least 3 seconds (except with "natychmiast"). After a wrong answer the pin turns red, and the child taps the green place to continue.

• The settings choose the continents (Europe by default) and the kinds of places (all by default). A place belongs to the continent it lies on, not to that of its country. Europe and Asia meet along the Ural Mountains, the Ural river, the Caspian Sea and the Kuma-Manych Depression, as taught in Polish schools: Moscow and Istanbul are in Europe; Novosibirsk, the Caucasus, Elbrus and Cyprus are in Asia; Hawaii is in Oceania. A sea on a border belongs to one continent: the Mediterranean and the Black Sea to Europe, the Caspian Sea to Asia, the Red Sea to Africa.

• Three settings under "Map" change how the map looks. "First view" shows either the whole continent (the default) or the region the place lies in, such as Scandinavia, the Middle East or Poland (see The map). "Thick country borders" draws the borders as solid dark lines instead of thin dashed ones. "Country names" writes the names of countries on the map in capitals, as many as fit without overlapping, the larger countries first. A name that would give the answer away is left out: when the island of Cuba is asked, the map has no "CUBA". The progress view uses the same borders and names.

The map

Each continent has its own map in the Lambert azimuthal equal-area projection, centred on the continent, so areas keep their size. The land of the continent is coloured by height, as in a school atlas (below 200 m, then from 200, 500, 1500 and 3000 m); other land is grey, and ice white. Lakes, rivers and borders are drawn, but no names, except the names of countries when that setting is on. More than 100 degrees from the middle of a map the projection squeezes the land into slivers, so the map stops there. The first view shows the whole continent, and the map can be moved 40% of that view beyond it, for places such as Spitsbergen.

With "First view" set to "region", the first view shows the box around one of 30 regions: Poland, the Low Countries, the British Isles, the Nordic and Baltic countries, Western, Central, Southern and Eastern Europe; the Middle East (with Turkey and the Caucasus), Iran, Central Asia, South Asia, East Asia, Southeast Asia and Northern Asia; North, West, Central, East and Southern Africa; Mexico and Central America, the Caribbean, the United States, and Canada with Alaska and Greenland; the north and the south of South America; Australia, New Zealand, Melanesia and Polynesia. A place belongs to a region when the point where its name is written lies inside the outline of the region and the whole place fits in its box. Places too large for one region, such as the Alps, the Danube or the Sahara, and all places in Antarctica, are shown on the map of the continent. The map of a region can still be zoomed out and moved over the whole continent, and the button with four corners goes back to the region. On a wide screen, a tall region such as the Middle East shows much land on its sides, since the box has to fit the height of the screen.

The map comes from Natural Earth (public domain): the land at 1:10 million, simplified to about 2 km, and lakes, rivers, ice and borders at 1:50 million. The heights come from ETOPO1 (NOAA, public domain). The shapes of the places come from Natural Earth too: lakes, rivers, seas, mountain ranges, deserts and island groups as outlines, islands as their land on the map. The lakes and rivers that are places are drawn on the map as well. Cities, peaks and a few small places are points, at their coordinates in Wikidata. The Karun and the Zayandeh River are not in Natural Earth: their courses were traced by hand through the towns on their banks and are accurate to some 10 km. The names in the five languages come from Wikidata, some corrected by hand. Country names are written where Natural Earth places them (countries at 1:50 million), with the names of StoliceMax; for lands that are not countries in StoliceMax, such as Greenland, Taiwan or Antarctica, the names come from the browser.

tools/make_maps.py downloads these data and writes maps.js (about 640 KB) and places.js (about 190 KB) from the list in tools/places.txt:

python3 tools/make_maps.py DATA_DIR

It needs Python with pyshp, shapely, numpy, scipy, scikit-image and requests, and keeps the downloads in DATA_DIR. python3 tools/make_maps.py DATA_DIR check lists each place with its Wikidata id and names, to check them by eye.

Rewards

The shop sells atlases, maps and globes, some ordinary and some famous from history:

Reward	Made	Coins
Treasure map		30
School globe		50
City map		70
School atlas		100
Celestial globe		125
Peutinger Map (Tabula Peutingeriana)	Roman Empire	150
Al-Idrisi's map (Tabula Rogeriana)	Palermo, 1154	175
Catalan Atlas	Majorca, 1375	200
Piri Reis map	Gallipoli, 1513	250
Mercator's Atlas	Duisburg, 1595	300
Blaeu's Atlas Maior	Amsterdam, 1662	350
Illuminated globe		400
Behaim's globe (Erdapfel)	Nuremberg, 1492	475
Jagiellonian Globe	Kraków, about 1510	550
Golden globe		650

All 15 together cost 3875 coins; learning all 480 places to the mastered level pays 8160, plus 10 for each finished day. The Jagiellonian Globe, kept at the Jagiellonian University in Kraków, is one of the oldest globes that show America. Buying one sends a paper plane across the screen for 4 seconds: it leaves its route behind as a dashed line, and pins drop onto the route one after another, each with a ring where it lands. With reduced motion switched on in the device settings, only the reward is shown. The rewards and their prices are set in ATLASES in index.html, the drawings in ATLAS_ART, the names and where the famous ones were made in i18n-maps.js.

AstronomiaMax

AstronomiaMax teaches facts about astronomy: mostly about the Solar System, and some about stars, galaxies and spaceflight. It runs in the same page as the other apps and has the same options.

• Each card is a question with a picture (an emoji), and the child picks the answer from four. There are 284 questions in six topics: the Sun; planets; moons; dwarf planets, asteroids and comets; stars and galaxies; and discoveries and spaceflight. For example: which planet is the hottest (Venus), how long sunlight takes to reach Earth (8 minutes), which way the tail of a comet points (away from the Sun), and who was the first Pole in space (Mirosław Hermaszewski). Facts that change with new discoveries, such as the number of moons of Saturn, are left out.
• A question either has three wrong answers of its own, or the app picks three other answers of the same kind: other planets, other moons, other astronomers. A question of the second sort must have only one right answer among all the answers of its kind. Where that is not so, the question has its own wrong answers: from sunrise to sunrise, a day on Mercury lasts two of its years, so the question about the planet whose day is longer than its year (Venus) does not offer Mercury, and the question about the Polish astronomer who said that Earth goes around the Sun (Copernicus) does not offer Hevelius or Wolszczan. Numbers are written by the browser in the language of the page, with their units ("8 minut", "۸ دقیقه").
• As in StoliceMax, a right answer the first time is never Easy. A question and four answers take a while to read, so Easy needs a right answer within 8 seconds, and a right answer counts as Hard only after 15 seconds instead of 10. The default time limit is 30 seconds, and 5 new questions a day. All topics are on by default.
• The progress view has a square for each question, with its picture, by topic.
• The review log uses the number of the question in astronomy.js as card_id, and has the question (a17) and the answer picked: the question for the right answer, or the question followed by # and the wrong answer (a17#venus, a3#8 hour).

The questions and answers are in astronomy.js, in the five languages. They were written for this app and have not been checked by a teacher.

Rewards

The shop sells trophies with a body of the Solar System on top instead of a cup: the Moon, the eight planets, Pluto (the ninth planet of older school books) and the Sun. Each stands on a dark base with a metal plate, and the body sits in a small dish on top of the stem. Under its name the shop says what the body is: Earth's moon, a planet, a dwarf planet (Pluto, since 2006) or a star.

Trophy	Metal	Coins
Moon	bronze	30
Mercury	bronze	50
Venus	bronze	75
Earth	silver	100
Mars	silver	125
Jupiter	silver	175
Saturn	gold	225
Uranus	gold	275
Neptune	gold	325
Pluto	gold	400
Sun	gold	600

All 11 together cost 2380 coins; learning all 284 questions to the mastered level pays 4828, plus 10 for each finished day. Buying one launches a rocket. It flies up from the bottom of the screen in loops around the new trophy and leaves a trail of dust behind, with some glittering stardust in it. The dust gathers over the trophy, and the trophy fades out while it is hidden. When the dust has cleared, about 5 seconds after the purchase, the trophy and its message are gone. With reduced motion switched on in the device settings, only the trophy is shown. The trophies and their prices are set in PLANET_TROPHIES in index.html, the drawings of the bodies in PLANET_ART, the names in i18n-astronomy.js.

BiologiaMax

BiologiaMax teaches facts about living things: animals, plants and fungi, the human body, cells and microbes, life in nature, evolution, and the scientists who found these things out. It runs in the same page as the other apps and has the same options.

• As in AstronomiaMax, each card is a question with a picture (an emoji), and the child picks the answer from four. There are 163 questions in eight topics: families and relatives; animals; plants and fungi; the human body; cells, genes and microbes; life in nature; evolution and extinct animals; and discoveries and scientists. For example: which family the giant panda belongs to (the bears), which part of the plant a potato is (the stem), how many hearts an octopus has (3), which kingdom sea sponges belong to (animals), which wild animal the cow comes from (the aurochs, the last of which died in Poland in 1627), the only country where the Asiatic cheetah still lives in the wild (Iran), and who wrote The Canon of Medicine (Avicenna).
• A question either has three wrong answers of its own, or the app picks three other answers of the same kind: other organs, other vitamins, other continents, other scientists. A question of the second sort must have only one right answer among all the answers of its kind. Numbers are written by the browser in the language of the page, with their units ("5 litrów", "۳۷ درجهٔ سلسیوس").
• The first topic asks for the families of species where the answer is a surprise, with wrong answers chosen by hand: the orca is a dolphin and not a rorqual or a shark, the giant panda a bear and not a raccoon, the dodo a pigeon, people are great apes, the horse chestnut belongs to the soapberry family and the sweet chestnut to the beech family, the lime tree and cacao to the mallow family, vanilla is an orchid, and the peanut is a legume and not a nut. Each family has its name in the language of the page with its Latin name under it ("Psowate", Canidae). Once answered, the card also shows the Latin name of the species (Ailuropoda melanoleuca); it is hidden until then because a family is named after one of its genera and the name often gives it away.
• A picture shows the subject of the question, or a symbol for it where no emoji shows it well: a stopwatch for the fastest runner, a magnifying glass for the smallest bird. A picture never gives the answer away: the hardest substance in the body (tooth enamel) has a diamond, not a tooth. Only emoji up to Emoji 13 (2020) are used, as newer ones such as 🪿 (goose) or 🫎 (moose) show as empty boxes on some tablets.
• As in AstronomiaMax, a right answer the first time is never Easy, Easy needs a right answer within 8 seconds, and a right answer counts as Hard only after 15 seconds instead of 10. The default time limit is 30 seconds, and 5 new questions a day. All topics are on by default.
• The progress view has a square for each question, with its picture, by topic.
• The review log uses the number of the question in biology.js as card_id, and has the question (o11) and the answer picked: the question for the right answer, or the question followed by # and the wrong answer (o11#procyonidae, ).

The first BiologiaMax asked only for the families of 238 organisms. Twenty of those cards are kept as the questions of the first topic, under their old numbers, so what was learned on them carries over; the others are no longer asked, but their coins and the specimens bought stay. Opened for the first time after the change, BiologiaMax switches on all the new topics and raises a time limit still at the old default of 20 seconds to 30.

The questions and answers are in biology.js, in the five languages. They were written for this app and have not been checked by a biology teacher.

Rewards

The shop sells specimens for a natural history collection: feathers, a shell, teeth, bones and fossils, each on a wooden base with a brass plate. Under its name the shop says which animal it comes from or, for a fossil, how old it is.

Specimen	From	Coins
Jay feather	Eurasian jay	30
Fish skeleton	common carp	45
Shark tooth	great white shark	60
Nautilus shell	nautilus	80
Peacock feather	Indian peafowl	100
Deer antler	red deer	125
Amber with a butterfly	40 million years old	150
Ammonite	150 million years old	180
Trilobite	400 million years old	210
Dinosaur bone	150 million years old	250
Sabre-toothed cat skull	20,000 years old	300
Mammoth tusk	30,000 years old	350
T. rex tooth	66 million years old	400
Megalodon tooth	5 million years old	475
T. rex skull	66 million years old	600

All 15 together cost 3355 coins; learning all 163 questions to the mastered level pays 2771, plus 10 for each finished day. Buying one sets off a swarm of butterflies, in the colours of a monarch, a morpho, a brimstone and other butterflies, that flies up from the bottom of the screen. Small groups of them land on the text and buttons on the screen, such as the specimens in the shop, and carry them off the top, swaying; a last group carries off the message with the new specimen. When the swarm has gone, about 5 seconds after the purchase, what they carried floats back down into its place. Only what is shown moves, not the layout of the page, and what is carried cannot be tapped while it is away. With reduced motion switched on in the device settings, only the specimen is shown. The specimens and their prices are set in SPECIMENS in index.html, the drawings in SPECIMEN_ART, the names and where they come from in i18n-biology.js.

Collection and gifts

The button with the latest reward in the header opens the collection: the rewards of all the apps, by app, with the number in each. A reward in the collection, or on the list in the shop, opens large, and from there it can be given away.

• Giving. "Podaruj" (give away), then a second tap to confirm, opens the share menu of the device with a gift link, for example to send it in a message. Without a share menu, the link is copied. Once the link is out, the reward leaves the collection and the link stays on show, to copy again. Closing the share menu without sharing keeps the reward. Coins are not given back. The device that gave the reward cannot take it back by opening the link.
• Receiving. Opening a gift link starts the app of the gift and puts the reward among its rewards, with the same celebration as buying it and "Prezent dla Ciebie!" (a gift for you). Shown large, it says when it was received. One link is received only once on a device.
• Pasting a link. A link opens in the browser, which on an iPad keeps its own progress, separate from the app added to the home screen. The collection therefore has a field "Odbierz prezent" (receive a gift) where a gift link can be pasted.
• Trading is two gifts, one each way.

A gift link is the address of the app followed by #gift/<app>/<reward>/<code>, for example #gift/capitals/eiffel/k3f9q. The code is random; it only keeps the same link from being received twice on one device, or on the device that gave it. Nothing checks that a link comes from a real gift, so anyone can write one for any reward: gifts are for fun, not safe against cheating.

Moving progress

Progress is saved in the browser, so each device and each browser keeps its own. On an iPad, Safari and the app added to the home screen also keep separate progress. The "Postępy" (Progress) section of the settings moves progress from one to another as a file:

• Saving. "Zapisz postępy do pliku" (save progress to a file) downloads one file with the progress and settings of all the apps, MaxApki-<date>.json, including the rewards in the collection. An app is in the file once a card has been answered or a setting changed in it. The file then has to be moved to the other device, for example by AirDrop or e-mail.
• Loading. On the other device, "Wczytaj postępy z pliku" (load progress from a file) opens a file picker. The app says when the progress in the file was saved and which apps it holds, and warns when this device has answers or rewards newer than those in the file. The file is stored only after "Zastąp postępy" (replace progress); the app then starts again with it.

Loading replaces the progress of each app that has progress in the file: its cards, coins, rewards (bought or received as gifts), review log and settings. An app in the file with no card answered and no reward brings only its settings, and keeps its progress on this device. Apps that are not in the file keep their progress and settings on this device. The open app, the language and the other choices saved under max-apps come from the file, while the apps opened and the codes of gift links from both devices are kept. This is a copy, not a sync: answers given on two devices are not merged, so practise on one device at a time and move the progress each time you switch.

The file holds JSON: { "maxapki": 1, "saved": <time>, "data": { <storage key>: <saved value> } }. Loading checks what is in the file, not its name, so a file saved with the earlier .txt extension still loads.

Moving to maxapki.top

MaxApki moves from https://grzegorz.chrupala.me/Anki/ to https://maxapki.top/. The browser keeps progress separately for each address, so the app at the old address sends it to the new one (move.js; the design is in docs/new-address.md):

• At the old address. On its first start with internet once the new address answers, the app goes to https://maxapki.top/#move/<data>, where <data> is the progress file (with the connection to the backup on GitHub, token included), compressed with gzip and written in base64url. The part after # is not sent to a server. From then on the old app saves nothing and only says that MaxApki has moved. Its buttons send the progress again, or save it to a file. A device with too much progress for a link (over 2 MB) moves it as a file.
• At the new address. The progress is stored at once if there is none there yet; otherwise the settings say what it holds and ask, as for a file. The same move is not stored twice. The backup on GitHub carries on as the same device, unless the new address is connected already. Until the app runs installed from the new address, each start asks to install it and to remove the old one (press and hold its icon, "Uninstall").

So that the two installed apps can be told apart, the app at the new address is called "MaxApki.top" and its icon has a deep blue background; the old one keeps the name "MaxApki" and the rainbow icon. The name (manifest.webmanifest, apple-mobile-web-app-title) and the icon (icons/) are changed only in gchrupala/maxapki: at the old address they would change the installed old app too.

On an iPad, the app added to the home screen keeps its own storage, so the progress has to be moved as a file there: "Zapisz postępy do pliku" on the moved screen of the old app, then "Wczytaj postępy z pliku" in the settings of the new one.

Backing up to GitHub

The "Kopia na GitHubie" (backup on GitHub) section of the settings keeps a copy of the progress in a private GitHub repository. The copy is the file that "Zapisz postępy do pliku" saves, stored as <person>/maxapki.json. Each backup is a commit, so the repository keeps every earlier version. It follows the GitHub sync of Myo.

One repository can hold the data of several people and several apps. Each person has a folder, and each app a file in it:

zosia/maxapki.json
max/maxapki.json
grzegorz/myo.json

The folder is the name entered when connecting, in lower case, with anything other than letters and digits turned into a hyphen ("Grzegorz Chrupała" becomes grzegorz-chrupała). Myo uses the same rule, so the same name gives the same folder in both apps.

Setting it up, on each device:

1. Create a private repository, for example app-data: github.com/new?name=app-data&visibility=private, or use one that already holds the data of other people or apps. A public repository is refused.
2. Create a fine-grained personal access token: this link fills in the name, a one-year expiry and the "Contents: Read and write" permission. Under "Repository access", choose "Only select repositories" and that repository. A fine-grained token can only reach repositories of the account (or organization) that made it, so for a repository in your account you make the tokens of all its users. One token can serve all the apps on a device.
3. In the settings, enter the repository as owner/name, the name of the person and the token, then tap "Połącz" (connect).

The app backs up a minute after the last change (an answer or a setting), when it is left, when it is opened or brought back, and when the device gets back online, but only if the progress changed since the last backup. Without internet it waits. "Zrób kopię teraz" (back up now) backs up at once. A backup takes two calls to the GitHub API: one looks up the version of maxapki.json in the list of files in the folder of the person, the other writes the whole file. If something else is written to the repository at the same moment, such as the data of another app, GitHub refuses the write and the app tries again, up to three times.

"Przywróć z kopii" (restore the backup) fetches the backup and then works like loading a file: the app says when the backup was saved and which apps it holds, and stores it only after "Zastąp postępy" (replace progress). An earlier version can be downloaded from the history of <person>/maxapki.json on GitHub and loaded with "Wczytaj postępy z pliku".

Progress from two devices cannot be merged, so the app does not replace a backup made on another device of the same person. Each device has a random name, which goes into the backup, and remembers the version of the backup it last wrote or restored. If the backup has changed since then and was made on another device, backups stop and a message says so once. The settings then show the date and apps of that backup with two choices: restore it here, or "Zastąp kopię" (replace the backup) with the progress of this device. To move to another device, connect it to the same repository with the same name and restore the backup there. A maxapki.json without a device name, such as a progress file put in the repository by hand, also waits to be restored or replaced.

The repository, the token and the state of the backup are saved on the device under their own key, max-backup, so the token goes neither into progress files nor into the backup. "Odłącz" (disconnect) removes the token; the backup and the progress stay. The token can read and write only the repository it was made for, but all of it: GitHub has no permissions per folder, so whoever has a token for a shared repository can read and overwrite the data of everyone in it. Share a repository only within a family; other people need their own. Anyone holding the unlocked device could read the token with the developer tools of the browser. When it expires, GitHub refuses it and the app says so; a new token then has to be made and connected.

How the page holds several apps

APPS in index.html describes each app: its name, the key its progress is saved under, its default settings and its rewards. CHOICE holds what differs between StoliceMax, ChemiaMax, LiteraturaMax, JęzykiMax, AstronomiaMax and BiologiaMax, the apps where the child picks one of four answers. MapkiMax has an entry there too, for what it shares with them (the continents and the review log), but no answers to pick from. Parts of the page that belong to some of the apps carry data-app with their names (times, capitals, chemistry, literature, languages, maps, astronomy, biology) and are hidden while another app is open. i18n-capitals.js, i18n-chemistry.js, i18n-literature.js, i18n-languages.js, i18n-maps.js, i18n-astronomy.js and i18n-biology.js have only the text that differs in those apps; the page puts it over the text of i18n.js. The open app, the language, the apps opened, the number of apps the menu was last seen with and the codes of the gift links received and given are saved under their own key (max-apps). The collection reads the rewards of the other apps from what they saved.

Tests

tests/srs.test.js replays review sequences through srs.js and compares stability, difficulty and intervals with the values py-fsrs produces (tests/fsrs_reference.json). To regenerate that file, run python tests/make_fsrs_reference.py with the fsrs Python package installed.

tests/move.test.js checks move.js: a move link made and read back with Polish and Persian letters, links that are not a move, a year of practice that fits in a link and too much that does not, which connection to the backup is kept at the new address, and the text of the move in every language.

tests/backup.test.js checks backup.js against a stand-in for the GitHub API: repository names, the folder names of people, base64 of Polish and Persian text, the first backup into an empty repository and the backups that replace it, a backup from another device that is not replaced without asking, a backup whose answer from GitHub got lost, people and apps sharing a repository, a write at the same moment that is tried again, files over 1 MB, and errors such as an expired token or a public repository.

tests/countries.test.js checks the StoliceMax data and text: 194 countries, each with a country and capital name in every language, at least four countries per continent, no two capitals with the same name on one continent, and the StoliceMax and app menu text in every language. tests/chemistry.test.js does the same for ChemiaMax: one formula and number per card, formulas made of element symbols, names in every language with no two alike, at least four cards per group, and the ChemiaMax text. tests/literature.test.js checks the LiteraturaMax data and text: one number per book, every author known and from a country with a flag, names and titles in every language with no two alike, books by at least four authors in each category, and the LiteraturaMax text. tests/languages.test.js checks the JęzykiMax data and text: one id and number per card, every kind of card at every level in every language, three different wrong answers for each gap and question and one gap per sentence, answers whose length does not give the right one away (picking the longest, the second longest and so on is right on at most a third of the gaps and questions), the concepts each gap and question uses, every picture word in at least two gaps or questions, the meaning of each card in the other interface languages (one row of translations per card, so none is shifted), no picture or word twice, at least four pictures per theme, and the JęzykiMax text. For the cards answered in the child's own words, it also checks that each is built on a card of its language, that its answers are short and count as right when written or said, that no definition holds its answer, that definitions and questions are translated, and that article cards ask the articles of their language (or ten, ta and to) of a noun in the singular. tests/answer.test.js checks how answer.js judges written and spoken answers. tests/maps.test.js checks geo.js (decoding, distances, the projection) and the MapkiMax data and text: one id and number per place, names in every language (Persian ones in Persian letters), at least 20 places of each kind and five kinds on each continent, places in Iran, Poland and the Netherlands, every place within reach on the map of its continent (cities and peaks in its first view), every layer of the base map, every region with places of its own continent inside its outline, a label for every country, and the MapkiMax text. tests/astronomy.test.js checks the AstronomiaMax data and text: one id and number per question, every question in every language (Persian ones with Persian digits) with no two alike, a text for every answer in every language, four different answers for each question, a question without wrong answers of its own only where its kind has at least four answers with different names, at least 10 questions per topic, and the AstronomiaMax text. tests/biology.test.js checks the BiologiaMax data and text as tests/astronomy.test.js does for AstronomiaMax, and also a picture no newer than Emoji 13 for every question, Latin names of species and families, and four different answers for every question in every language.

Limitations

• Progress is stored in the browser's localStorage, so it stays on one device and one browser unless it is moved as a file (see Moving progress) or through the backup on GitHub (see Backing up to GitHub). It is not synced, and answers given on two devices are not merged. Progress from the earlier SM-2 version of the app is not carried over.
• The app uses the default FSRS parameters, which were fitted on Anki users in general, not on children. There is no optimizer in the app; the review log has to be exported and fitted elsewhere.
• The 3-, 4- and 10-second thresholds are guesses and have not been tested with children.

Files

• index.html: the eight apps (layout, styles and interface code).
• i18n.js: the interface text in Polish, English, Dutch, Spanish and Persian.
• i18n-capitals.js: the text that differs in StoliceMax.
• countries.js: the countries and capitals of StoliceMax.
• i18n-chemistry.js: the text that differs in ChemiaMax.
• chemistry.js: the compounds of ChemiaMax.
• i18n-literature.js: the text that differs in LiteraturaMax.
• literature.js: the books and authors of LiteraturaMax.
• i18n-languages.js: the text that differs in JęzykiMax.
• languages.js: the French, Spanish, Dutch, Italian and Polish cards of JęzykiMax.
• languages-translations.js: what the cards of JęzykiMax mean, in the languages of the interface.
• languages-recall.js: the cards of JęzykiMax answered in the child's own words, and the article cards.
• move.js: the move link that takes the progress from the old address to https://maxapki.top/. It works in the browser and in Node.
• CNAME: the address GitHub Pages serves the app at, maxapki.top. It is only in gchrupala/maxapki, never in gchrupala/Anki.
• docs/new-address.md: the design of the move to https://maxapki.top/.
• answer.js: whether an answer written or said in the child's own words is right. It uses voice.js and works in the browser and in Node.
• i18n-maps.js: the text that differs in MapkiMax.
• i18n-astronomy.js: the text that differs in AstronomiaMax.
• astronomy.js: the questions and answers of AstronomiaMax.
• i18n-biology.js: the text that differs in BiologiaMax.
• biology.js: the questions and answers of BiologiaMax.
• places.js: the places of MapkiMax, with their names and shapes.
• maps.js: the base map of MapkiMax: land, heights, ice, lakes, rivers and borders, the outlines of the regions, and where country names are written.
• geo.js: the map projection, the encoded lines of and , and distances on the Earth. It has no dependencies and works in the browser and in Node.