SEREN

A three-lane arcade racer that runs in a browser tab. Nine cars, each with its own ultimate, race up a road that never stops speeding up — through a city, a desert and a rainbow strip of deep space — dodging puddles, meteors and tumbleweeds, grabbing items out of mystery bubbles, and barging each other into the barriers.

No install, no build step, no dependencies. One HTML file, one stylesheet and fifteen JavaScript files, drawn entirely with hand-written Canvas 2D.

▶ Play it · a game by hiyroscript

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Contents

• Playing · Controls · Modes
• The cars and their ultimates
• Driving · Contact rules
• The road · Hazards · Mystery bubbles and items
• Conditions · Race structure · Difficulty
• Local multiplayer · Settings and saved data
• Accessibility · Browser support
• Running it locally · Project layout · Deploying
• Known quirks

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Playing

Open the page, pick a language the first time, then Start race. Pick a mode, pick a car, and the lights go out three seconds later.

Cars & more on the home screen is the reference: every car's ultimate, every track, every trap, the mystery-bubble drop odds, and what each Condition means. It is the in-game manual and it is built from the same tables the race reads, so it can never drift out of date.

The HUD, clockwise from the top left: the track name and race clock; the distance you have covered and the nine-car standings, with your row picked out; a ladder down the right showing how far ahead or behind each racer is; your ultimate meter and item box bottom right; your own Conditions as a column of coloured icon circles bottom left; three pink, yellow and cyan shield bars immediately above the boost rail at the lower-left; and the boost bar across the foot. Racers off the top or bottom of the screen get an edge badge with their lane and the gap in metres — or, past 500m, a pair of chevrons on the ladder.

Controls

Keyboard

Key	Does
← → or A D	change lane (and barge whoever is in it)
↑ or W — hold	boost
Shift or Space	ultimate
E	use the item you are holding
P or Esc	pause / resume
Space / Enter on a menu	take the obvious next step (and pick a random car on the car sheet)

Touch and mouse — on the canvas

Gesture	Does
swipe left / right	change lane — a held drag keeps stepping across
swipe up and hold	boost
press and hold one finger (0.35s)	ultimate
double-tap (within 0.5s)	use the item
tap the ultimate square / item box	ultimate / use item

The boost swipe latches until the finger comes off, so the travel you have already spent does not keep counting against the next lane change. The ultimate needs one finger held — a second finger on the glass suppresses it.

Controller — local play

Browsers report a "standard" mapping for PlayStation, Xbox and most third-party pads alike, so one table covers all of them.

Control	Does
left stick ← / → (or d-pad)	change lane
right stick held up (or d-pad up)	boost
both sticks clicked in (L3 + R3 / LS + RS)	ultimate
R2, or Circle (Xbox: RT, or B)	use the item
Options (Xbox: Menu)	pause
Cross / Options on a panel	resume, or race again
Circle on a panel	leave the race

Everything is edge-triggered off a per-player snapshot of the previous frame, so a held trigger fires once and a held stick walks across the lanes at a readable pace.

Modes

Endless — no finish line. Five bots on the road with you and a road that keeps getting faster. Drive as far as you can; leaving the race banks the distance as your personal best.

Race against bots — pick a difficulty, then race the full distance: reach 3.00×, then three track changes, then 900 metres to the flag. Nine cars, every trap, every pickup, and a finishing order at the end.

Local play — two to four people on one screen, one controller each, on a computer. The screen splits into equal columns and the bots fill whatever seats are left, so it is always a nine-car field. Local play is offered on phones but greyed out with the reason, because it needs a keyboard-and-mouse machine with pads attached.

Local play then asks how you want to race:

• Standard play — the full game, with a difficulty for the bots.
• Custom play — set the road up your way: how many bots (from none up to however many seats the people leave free), and whether traps, mystery bubbles, boost, and ultimates are on the table at all.

Backing out of a custom setup and choosing standard restores the defaults, so you never inherit half a custom race by accident.

The cars and their ultimates

Every car has the same mechanical ultimate: a 85-second charge, then 15 seconds at 2× its own pace. Difficulty changes when a bot spends the boost, never its strength, duration or charge rate. All nine do something else with those fifteen seconds as well.

Car	Ultimate effect
Dhaval	15 seconds at 2× pace, five-level light Obscurity and destruction of contacted road hazards
Flann	15 seconds at 2× pace, on fire — see below
Neela	15 seconds at 2× pace, transformed — see below
Lolanthe	15 seconds at 2× pace, Mind Controlling — see below
Verdant	15 seconds at 2× pace, invisible — see below
Rhosyn	15 seconds at 2× pace, in Aero-Glow — see below
Saffron	15 seconds at 2× pace as an airborne metal dragon; meteor interception and a final touchdown impact

Flann's ram

For the whole fifteen seconds, Flann visibly catches fire and turns into a battering ram. It keeps the ordinary speed boost and the ordinary charge clock; what it gains is priority in a collision.

• Racers. Flann destroys racers it rear-ends or barges into. A racer hitting Flann receives the ordinary collision response. Two ulting Flanns cancel the special ram; Flann and ulting Verdant still mutually destroy each other regardless of initiator.

• Tumbleweed. Smashed apart on contact. No Slow and no meter cost.

• Meteor. Neither the falling rock nor the blast can destroy it, and the ultimate carries on.

• Puddle. Shield halves are preserved while the ultimate is active. Water is liquid and cannot be rammed apart, so an ulting Flann still gets the spray over its screen and still wears Obscured — Boosted and Obscured at the same time.

None of this is invulnerability. A respawning or finished racer is still out of reach in both directions, so a ram cannot spawn-kill or touch a recorded result, and two ulting Flanns cancel each other out and trade an ordinary shunt. The moment the fifteen seconds are up, Flann is an ordinary car again. No other car gets any of it.

Neela's exchange

For the whole fifteen seconds, Neela changes shape. It races as a blue craft with a long energy trail instead of as a car, and it keeps the ordinary speed boost and the ordinary charge clock. What it gains is one exchange and a hazard privilege.

• Racers. The first racer it touches while transformed is not wrecked. The two of you trade places: Neela ends up where that racer was standing at the moment of contact, and that racer is left where Neela was when the button went down — which by then is a long way back down the road. That ends the transformation on the spot, whatever is left of the meter. It is one exchange per ultimate and no more; from there Neela is a boosted ordinary car again, and racer contact goes back to the usual rear-end and barge rules.
• Tumbleweed. Smashed apart on contact, for the whole ultimate — before the exchange and after it. No Slow and no meter cost.
• Meteor. Neither the falling rock nor the blast can destroy it, again for the whole ultimate.
• Puddle. Shield halves are preserved while the ultimate is active. Water is liquid and cannot be smashed, so an ulting Neela still gets the spray over its screen and still wears Obscured.

The transformation and the exchange white out the view of each human involved for a moment — Neela's own on activation, both racers' on the exchange — and both cars flash white as they change place. In local play that white belongs to the column it happened in: it never touches the seat next door. The white is visual only. The race does not pause, the meter does not stop, the controls still answer, and the car is steered by the person or the bot driving it throughout. There is no homing and no auto-steer: the exchange happens where the cars actually meet.

None of it is invulnerability either. A respawning or finished racer is out of reach in both directions, so an exchange cannot spawn-kill or touch a recorded result; two transformed Neelas cancel each other out and trade an ordinary shunt; and Neela never gains the ability to wreck anybody. The moment the fifteen seconds are up, it is an ordinary car again.

Lolanthe's mind control

For the whole fifteen seconds, Lolanthe takes the road with it. A single queen_note.PNG floats above the car, upright and gently rising and falling, and everything close enough loses its driver.

• The aura. Every other racer within about four car lengths along the road is Mind Controlled, in any of the three lanes. It is a real debuff with a real badge, and it lasts three seconds from the last moment that racer was in range — a fresh hold resets those three seconds rather than adding another three, so standing in the aura keeps you held and never builds up a minute of it. Three pion_note.PNG icons orbit every racer it has taken.
• What it takes. Steering, boost, items and the ultimate button, for the person holding the controller, for a local seat and for a bot alike. What it does not take is the car: it keeps driving, its physics, its timed effects, its hazards, its wreck lifecycle and an ultimate it was already running all carry on. A driver already in its own ultimate keeps it; it simply cannot start anything new.
• The lane. Anything caught in Lolanthe's own lane is forced out of it — inward from a wall, either way from the middle. The destination does not have to be empty: whoever is in it is met through the ordinary barge, so the shove can shunt them across, wreck them against a barrier, run them into an ulting Flann or be swapped away by a transformed Neela. Chain reactions are the point. Lolanthe gains no kill from any of it — the destruction comes from the collision system, not from a ram Lolanthe does not have.
• Tumbleweed and meteor. Smashed apart on contact, for the whole ultimate, exactly as Neela's are. Puddle still obscures the view, but consumes no shield during the ultimate.

Lolanthe does not destroy racers by touching them. An ulting Verdant is immune to the whole of it, reveal included — Lolanthe cannot command a target it cannot see.

Verdant's invisibility

For the whole fifteen seconds, Verdant disappears — and only that. It is still physically on the road, still in the race order, still carrying its own measured hitbox, and still something you can run into.

• Who sees it. In its own driver's view it fades to 50%, so the person driving can still find their car. In every other view it fades to 0%. In local play that is worked out per column, so two, three and four players each get their own answer. The fade takes about a quarter of a second in each direction rather than snapping.
• Running into it. Any racer that initiates contact into an ulting Verdant is destroyed, and Verdant shows itself for a fifth of a second as it happens. The reveal is cosmetic: it does not cut the ultimate short and it does not hand Lolanthe a target.
• It running into you. Nothing. The defence works one way only: an ulting Verdant that rear-ends or barges into somebody gets the ordinary shunt and barge, not a kill.
• Two pair rules. An ulting Verdant and an ulting Flann destroy each other whichever of them arrived, and both meters end at exactly 0%. A transformed Neela meeting an ulting Verdant is destroyed with its meter emptied, no exchange and no teleport, and Verdant survives.
• Tumbleweed and meteor. Smashed apart on contact, for the whole ultimate. Puddle still obscures the view, but consumes no shield during the ultimate.

Nothing pinned to the car gives it away: the exhaust out of its pipe, its seat ring and flag, its Condition badges and its edge marker all follow the same per-view opacity, so another player's screen shows no outline of where it is. Its dot stays on the ladder, because it is still in the race. Bots do not get to see what a person could not: an ulting Verdant is out of their targeting, their lane reads and their threat picture, so they can blunder into one exactly as you can.

Rhosyn's Aero-Glow

For the whole fifteen seconds, Rhosyn's own driver is shown a different world — Aero-Glow, a black void streaked with luminous pink, with no rivals, no hazards, no bubbles and no scenery in it. Everybody else's road simply has no Rhosyn on it.

The thing to understand about it is what does not happen. There is never a second race. Rhosyn is not teleported away, not frozen, not put on a private coordinate system and not given a distance counter of its own, and the track the race is running is never replaced. The canonical racer goes on being advanced by exactly the same simulation as everybody else: it steers, it covers ground at the same 2× pace, it crosses track seams, it changes biome, it moves up and down the running order and it can cross the finish line. Aero-Glow is a private view over that one racer, plus the fact that the shared road cannot touch it.

• Going. The car floods white, the driver's screen flashes white, and the renderer changes worlds while the screen is covered. To everybody else the glowing white Rhosyn finishes its flash and is gone from the road.
• While it is away. Nothing on the shared road can reach it — racers, barges, Flann's ram, Neela's exchange, Verdant's defence, Lolanthe's aura, tumbleweeds, meteors, puddles, oil, seekers and bubble rows all pass it by — and it can reach none of them either, which is the point: Aero-Glow is not somewhere to attack the field from. An item it is holding is kept rather than spent. Boost, steering and the ultimate's own pace all work normally.
• Coming back. The view flashes white again, the renderer changes back, and Rhosyn reappears at the position the race has already carried it to — in whatever track the race has reached, which may not be the one it left. There is no teleport, no snap and no correction, because there is nothing to correct. To everybody else it returns through the matching white flash.
• The two seconds. At the moment it is genuinely back on the shared road it is granted the existing Invulnerable Condition for 2 seconds — the same badge, the same blink and the same protection a respawn gets, taken as max(existing, 2) so a longer protection is never shortened. There is no second shield and no Rhosyn-only immunity.
• Standings. Canonical race order continues. Other drivers keep their tracker; the Aero-Glow owner sees no distance, place rows or ladder until returning. Its ultimate meter remains visible, and its track label reads Aero-Glow.
• In local play. Per column, like everything else: one player can be in Aero-Glow while the other two or three carry on racing the real world in the same frame. Only that player's column flashes white and only that player's column changes worlds. A bot Rhosyn has no screen, so it simply vanishes from every human view while its canonical simulation carries on.

Saffron’s dragon

The orange base car uses two measured exhaust outlets. Its metal dragon uses six, spans two lanes, and rises above racers and hazards with a shadow at its canonical position. Steering, race distance, finish progress and Mind Control continue normally. Ground hazards and pickups are passed over without damage or collection. After the shared fifteen seconds, the normal car drops rapidly and resolves its measured-hull landing impact.

The ultimate meter

• 85 seconds from empty to ready, for every car in the field.
• Hitting a trap costs 5%; being wrecked costs 10%; wrecking somebody else pays 10% of the charge meter.
• During activation the meter counts down the fixed 15-second duration. Charge rewards and penalties do not alter this countdown, and another press does nothing. A wreck or finishing the race ends an active ultimate.
• Custom play can disable ultimates for every driver.

How ultimates interact

Saffron flies above road-level interactions, while remaining susceptible to Lolanthe’s Mind Control at canonical road distance. Falling meteors striking the dragon are intercepted without a ground explosion. At expiry Saffron transforms back in the air and drops onto its canonical position, wrecking each reachable racer overlapped by its normal-car hull. This never teleports its race distance.

Where they meet, the priority is fixed and in this order:

0. An airborne Saffron or absent Rhosyn on either side: there is no contact. It is first because it is not a priority at all — the other rules settle a contact between two bodies, and this one says one of the two bodies is not on this road.
1. An ulting Verdant and an ulting Flann destroy each other, both meters emptied, whichever of them arrived.
2. An ulting Verdant and a transformed Neela destroy the Neela, meter emptied, with no exchange.
3. Anything else that runs into an ulting Verdant is destroyed.
4. A transformed Neela exchanges places, ahead of Flann's ram — a Flann and a Neela meeting with no Verdant involved is the exchange rather than the kill, because the contact spends Neela's transformation either way.
5. An ulting Flann wrecks a racer it initiates contact with.
6. The ordinary shunt, barge, slow and lane-change consequences.

Lolanthe is nowhere in that list, because Lolanthe wins no contacts. Its forced lane change enters the list from the top as an ordinary barge made by the racer being pushed.

For every car, Slowed and other legitimate debuffs coexist with the speed multiplier, and only Boosted is added to the Conditions on show, with ordinary boost flames and a generic activation burst. Flann adds its body fire on top of those, and only for the ultimate: an ordinary boost or a boost can lights the exhaust and nothing else. Neela is the same the other way round — its blue energy exhaust is the ordinary boost flag every car has, so boosting, a boost can and the ultimate's own speed all light the pipes, and none of them transforms anything. Only the ultimate does that.

Obscured combines independent water and Dhaval timers into one badge. Transformation whiteouts also use this badge as presentation feedback; they are not hostile debuffs and Cleansed does not cancel transformations.

Mind Controlled is Lolanthe’s directly applied Condition. It is a debuff like Slowed and Skidded: temporary invulnerability refuses it and clears it, a wreck and the finish line take it away, and its badge is derived from the same three-second timer the control lock is.

Dhaval — light-show Obscurity

Dhaval is the eighth racer, using v_dhaval.PNG. Its ultimate covers nearby opponents’ own views in large white, purple, red and green moving, orbiting, popping light circles. Obscurity starts at level 1. Each accepted road-hazard contact adds one level, capped at 5; shield absorption still counts. Destroying a hazard with an ultimate, a near miss, and a Perfect Dodge do not escalate it. The four-car-length aura refreshes a three-second tail without resetting severity. A new episode after expiry begins at level 1.

Ulting Rhosyn and Verdant are immune and clear existing Dhaval Obscurity on activation. Ulting Lolanthe instead receives Cleansed: immediately remove all debuffs and refuse new ones for three seconds, refreshed by exposure. Cleansed does not prevent physical collisions, shield loss or wrecks.

Dhaval’s own ultimate destroys contacted weeds, meteors and puddles. Its shared charge, duration and pace are unchanged. Obscured bots have shorter sight and slower reactions. Reduced motion freezes the light layout while preserving its coverage. See measurements, interaction tests and visual QA.

Driving

Lanes. Three of them. Changing lane into an occupied one is a barge: if the other car has room it is shoved across and left labouring; if it is already against a barrier, the hit wrecks it. Either way the lane is yours.

Boost. A full bar lasts 5.5 seconds at 1.5× pace and takes 5 seconds to refill. Run it completely dry and it locks out until it is full again. It will not run while you are wrecked.

Rear-ending. Running into the back of the car in front shunts it forward for 0.8 seconds at 1.35× while you are left labouring. Both cars lose the same time to the bump, and the shunt shows on the shunted car as Boosted.

Wrecks. Being destroyed parks you for 3 seconds, then respawns you Invulnerable for 2 more. That is total — every debuff, hazard, trap and attack — and it phases, so you pass through anything that would otherwise meet you.

Contact rules

A car does not make road contact when it has finished, is wrecked, or is Invulnerable from a respawn. An ultimate grants none of these protections — including Flann's, which still has to physically meet what it destroys and is still refused by all three of them.

Finishing is not a Condition and it is not temporary Invulnerability: it is a race lifecycle state. The instant a car crosses the line it is out of play for the rest of that race. Nothing selects it as a target, nothing tracks it, nothing collides with it, and no debuff, item, hazard or seeker can alter the result it has earned — a seeker already locked on gives the mark up and burns out. All it does from there is roll out onto its parking mark.

The road

Three tracks, swapping every 60 seconds. Where two meet, the ground interlocks along a wandering seam rather than butting up against a line, and the driving surface fades over a stretch rather than at a step.

Track	Looks like	Hazard
City	Dark asphalt between pale rooftops, water tanks and helipads. White lane dashes, crosswalks and red hydrants along the kerb.	Puddle
Desert	Sand-coloured ground and layered rock, cacti and scrub on the shoulders. Sand drifts across a dark road under faded yellow markings.	Tumbleweed
Rainbow space	A road of scrolling rainbow bands over near-black, edged with neon cyan rails. Nothing beside it but a drifting starfield.	Meteor

The road begins at 1.00×, adds 0.10× every 20 seconds, and reaches 3.00× at 6:40. Actual road scrolling follows this pace, including scenery and hazards. The HUD shows the base multiplier to two decimal places.

Hazards

Every racer starts with three full shield bars: pink → yellow → cyan. Each puddle or tumbleweed hit outside an active ultimate removes half a bar, consuming cyan → yellow → pink, retaining its normal Obscured or Slow effect on a surviving racer. The sixth hit destroys the racer through the existing 3-second wreck lifecycle; it does not take a seventh hit. During the wreck delay the shield stays empty, and respawning fully restores all three bars, along with the existing temporary invulnerability. This applies equally to players, local humans and bots, with each local view showing its owner's bars.

Meteors bypass durability entirely: their existing destruction rules still apply, even at full shield, and they consume no shield halves. Other wreck sources also leave durability untouched until respawn. A hazard destroyed by an applicable ultimate costs no shield; protected racers and successful dodges lose none either. One puddle encounter can only consume one half, however long the racer overlaps it.

A perfect dodge grants +10 percentage points of ultimate charge: change steering with a real hull collision at most 120ms away, then escape safely. Early lane changes, wide or passive misses, hits, and repeated passes do not qualify. The same geometry and reward apply to players and bots. Protected, finished, wrecked, airborne or off-road racers cannot earn this reward.

Each collected Mystery Bubble grants +5 percentage points of ultimate charge, even while its item rewards remain disabled. Both rewards use the shared charge helper: they never extend an active ultimate’s remaining 15-second duration.

Hazard	Track	What it does	Ultimate cost
Puddle	City	Water over your screen: Obscured for 2.6 seconds	−5%
Meteor	Space	A blinking red ring marks the impact. Anything in the blast is destroyed and respawns after 3 seconds	−10%
Tumbleweed	Desert	Rolls across from either side; halves your speed for 1.7 seconds	−5%

A Flann with its ultimate running smashes the tumbleweed and shrugs off the meteor, at no cost to its meter. The puddle still gets it.

The meteor's ring is a spot on the road, not on your screen, and how long the rock has left is measured in seconds — so it lands where it was always going to land no matter what you do to your own speed. Every ultimate leaves the world clock and other racers’ speed unchanged.

The seeker clears hazards it passes through.

Mystery bubbles and items

Item rewards are switched off at the moment. Bubbles still drift across the road and are still collected, but nobody — you, a bot or a local seat — comes away holding a Boost can, Oily oil or a Seeker. Nothing has been removed: the items below are the items that come back when MYSTERY_ITEMS_ENABLED in js/data.js goes back to true, and everything in this section describes them as they were and will be. The custom-race mystery bubbles switch is a separate thing and still decides whether rows appear at all. Every collected bubble still grants +5 percentage points of ultimate charge.

Three bubbles drift across the road together, a row every 5,400–8,600 road units. Touch one for a random item and take as many of the three as you can reach — each new one replaces what you hold, and a trade flashes the box so a silent swap still reads.

Item	Rarity	Drop	Leading	What it does
Boost can	Common	66.7%	70.6%	2.2 seconds at 1.55× that does not touch your boost meter
Oily oil	Rare	27.8%	29.4%	Drops a slick behind you for 15 seconds. The first racer to touch it loses all grip for 4 seconds — reversed steering — and takes the slick with them
Seeker	Legendary	5.6%	—	A missile that hunts the leader, destroying whatever it passes through

The seeker never drops for whoever is leading; out in front, its share goes to the other two. Invulnerability, a wreck and the finish flag stop a seeker hit; an ultimate does not.

A row does not sit there forever. It flashes and goes on whichever comes first: the last stretch before it drops off the bottom, or a 30-second clock that only runs when the road has all but stopped.

Conditions

Seven of them, and each one is a small filled circle in its own colour with a plain device inside it. The shape carries the meaning as much as the colour does, so a Condition is never told apart by colour alone.

Condition		Colour	Icon	Meaning
Cleansed	buff	#94F4DD	sparkle and clearing star	Clears every debuff and refuses new ones for three seconds; physical contact still applies
Boosted	buff	#FF9A4A	forward chevrons	Anything making you go faster, whatever put it there: the boost meter, a boost can, an ultimate, or a rear-end shunt
Invulnerable	buff	#FFD86B	shield	Respawn protection: pass through road contact and refuse every debuff
Slowed	debuff	#8A9099	arrow brought down to a floor	Anything making you go slower, whatever put it there
Obscured	debuff	#B07A4A	crossed-out eye	Puddle water or Dhaval’s five-level light obstruction; also used for transformation feedback
Skidded	debuff	#0B0B0C	paired skid marks	No grip: left goes right and right goes left

| Mind Controlled | debuff | #8A4FE0 | musical note | Lolanthe locks driver commands and can force lane changes |

Where they are shown. Every visible car that is not the owner of the view you are looking through wears its Conditions as a compact column of these circles beside it — bots and other people alike, because what decides is the racer's state and never who is holding the controls. Your own car never carries them: yours go in the bottom-left corner of the HUD instead, as the same circles. In split screen this is worked out per column, so in Player 2's window Player 2 has corner badges and everyone else has beside-car ones, and in Player 1's window Player 2 is a rival and gets beside-car badges like anybody else.

Where several are active they stack in a fixed order — Invulnerable, Boosted, Slowed, Obscured, Skidded — so a stack never reshuffles between frames.

Invulnerable clears the debuffs already on you and refuses new ones for as long as it lasts. Rhosyn and Verdant clear Dhaval Obscurity on ultimate activation. Ulting Lolanthe converts Dhaval’s aura into Cleansed; other existing conditions keep their ordinary rules.

A racer that has crossed the line shows no Conditions at all: it is out of the race, not protected within it. The garage's Conditions tab is where the symbols are learned — Buff and Debuff on two sub-tabs, each card carrying the same circle you see on the road.

Race structure

Endless has no finish line — it runs until you leave.

Race against bots and local play run to a flag:

At 0:00 the pace is 1.00×. Each 20 seconds adds 0.10× until 6:40 / 3.00×, which arms the three-track closing sequence, followed by the +900m finish stretch. Elapsed time alone never starts the closing sequence. The HUD keeps the speed visible alongside T-3, T-2, T-1, then the metres remaining.

When the third track change lands, the flag is planted 900 metres ahead. Cars cross, are given a place, and roll out onto a staircase of marks past the line — first place furthest, each place behind stopping one step earlier, in alternating lanes — so the field parks in the order it finished. Finishers are out of play entirely: nothing can target or touch them.

On one screen the race ends when your car crosses. On four it ends when the last person crosses; bots still on the road finish behind, as they always do.

Difficulty

A difficulty is not a multiplier on anything the car does. Every setting drives the same car at the same pace off the same charge clock. What changes is how well the driver thinks.

	Easy	Medium	Hard	Brutal
Misses trouble in its own lane	52%	26%	10%	3%
Reaction time	0.70–1.40s	0.35–0.75s	0.18–0.42s	0.07–0.22s
Reconsiders the race every	0.50–0.95s	0.34–0.68s	0.22–0.46s	0.14–0.30s
Reads hazards this much further ahead	—	110	250	380
Projects other cars forward	—	0.35s	0.80s	1.30s
Overall competence	0.14	0.46	0.80	1.00
Picks targets deliberately	0.10	0.42	0.78	1.00
Defends its place	0.06	0.36	0.72	1.00
Values items and ultimates	0.10	0.46	0.82	1.00
Decision left to chance	50%	26%	11%	3.5%

In practice: Easy is slow to spot trouble and happy to let you by. Medium races you fairly and takes a lane when it needs one. Hard blocks, barges and times its ultimates well. Brutal misses nothing, defends every lane, and wrecks you if it can.

On top of difficulty, each car has a temperament — nerve, spite, patience and guard — that is jittered at the start of every race, so five bots on one setting are not the same bot five times, and the Flann you raced last time is not quite this one.

Bots only ever decide. The doing is handed straight back to the same functions your own inputs call, so a bot barging, dropping oil or spending an ultimate is running your mechanic, not a copy written for bots.

Local multiplayer

Two to four people, one controller each, on one computer. The flow is: player count → controller discovery → standard or custom → difficulty (or the custom sheet) → each player picks a car in turn with their own pad → race.

• The screen splits into equal columns, one per person. Each column is a full game — its own camera, its own instruments — and the world is built wide enough to cover the whole spread of the field, so a player half a screen up the road is not driving through nothing.
• The field is always nine cars. Bots fill whatever seats the people leave.
• Every human car wears a coloured ring on the road, and the cars that are not yours wear a numbered flag, so two players in identical positions on two columns can still be told apart.
• Cars are picked one at a time and a car already spoken for is dead on the board for everyone after. Backing out undoes one pick at a time.
• If a controller drops out mid-race the whole race pauses, every car lets go of everything it was holding, and the panel says whose pad it was. Reconnect it and carry on.
• Local play reads the personal best but never writes it — four people on one machine do not share a record.

Settings and saved data

The sliders icon in the top right of the home screen opens Settings, a panel over the moving road with every preference in it:

Group	Setting	Does
General	Language	English or Français, applied to the whole interface as you press it — the panel included, and without a reload
Audio	Sound	On or off, the one switch for every sound the game makes
Audio	Master volume	0–100%, straight on to the master gain, live
Accessibility	Reduced motion	System / Reduced / Full
Accessibility	High contrast	System / On / Off
Interface	Show control hints	The keyboard row along the bottom of the home screen

At the foot is Restore default settings, which asks once and then resets those preferences only — your language and your personal best are kept.

Six values in localStorage, and nothing else is ever written:

Key	Holds
seren.lang	en or fr
seren.sound	1 or 0
seren.volume	0–100, default 90
seren.motion	system, reduced or full
seren.contrast	system, on or off
seren.controlHints	1 or 0
seren.best	your furthest distance, in metres

Existing saves from the previous name are copied from redline.* on startup when the corresponding seren.* value is absent. Existing Seren values take priority, and the old keys remain as a backup. All new saves use seren.*. A saved value that is not one of the ones listed above — an older build, a hand edit — falls back to its default rather than reaching the game.

If localStorage is unavailable — a private window, blocked site data — the game falls back to an in-memory store and keeps working for the session.

Language. English and French. The first visit asks before anything else; after that it lives in Settings.

Sound. All generated with the Web Audio API — no audio files. The context is created lazily on your first interaction, so browsers never refuse it for starting outside a user gesture. Everything plays through one master gain, which is the volume when sound is on and silence when it is off.

The interface

One system, from the splash to the finish line, built on four things:

• Black, white, grey, red. The ground is near-black, the type is white through a tight neutral ramp, and red is the only accent — the primary action, the selected step, the charge in the ultimate square, the tick beside your own row in the standings. Colours that mean something in the game — the four seat colours, gold/silver/bronze in the running order, the rarity of a pickup, the seven Condition colours — stay, because they are the game speaking and not the interface decorating.
• Glass for anything elevated. Dialogs, panels, the countdown plate and every instrument over the road use one recipe: a dark tonal fill, a blurred backdrop, a hairline edge and a highlight along the top. Where a browser cannot blur, the same surfaces go opaque instead of translucent, so readability never depends on the effect. Nothing else is glass — the hierarchy from ground to surface to control to overlay is what the treatment is for.
• Five type roles and no more. Archivo for display and actions, IBM Plex Sans for copy, IBM Plex Mono for metadata and every readout. Numbers are tabular everywhere they can change.
• One geometry. A single radius scale, a single spacing scale, and one focus ring — a white outline over a dark halo, so it is visible on glass, on red and on the moving road alike.

Menus use distinct compositions: an angled scrolling road and oversized wordmark on Home, three mode destinations, a numbered difficulty scale, equal-column player previews, live controller bays, a rule workbench, and a car showroom. The showroom uses the actual car renderer; hovering or focusing inspects a car, and choosing it keeps the original direct-pick behavior. Local setup displays the player roster and current configuration. Cars & More uses a reference index with keyboard-operable tabs. Setup occupies the viewport; the game retains its original race layout.

The race HUD is the same system rather than a second one. The corners hold what you consult: the pause button and the track and clock top left, distance and the running order top right. The bottom holds what you spend: the boost meter in its tray, three shield bars just above it on the left, your Conditions above those, the ultimate and item squares on the right. On a wide window that bottom band closes in on the road instead of stretching to the far corners, so it stays in peripheral vision. The ultimate square fills from the foot as it charges, so the reading is a shape before it is a number.

Local play draws the same instruments on the canvas, once per column, from the same constants — see the HUD section of ARCHITECTURE.md.

Accessibility

• Reduced motion. prefers-reduced-motion: reduce flattens the page's animations, and Settings can overrule it either way — Reduced stills the interface on a device that never asked, Full restores the animation for a player who would rather have it. Things drawn frame-by-frame on the canvas sit outside CSS, so they ask the same resolved answer — the item-box swap flash, for instance, becomes a brightness pulse with the box held still. Every state that is normally carried by movement also has a still form: a charged ultimate stays red, your row in the standings stays ticked, a Condition badge appears without animating in.
• Never colour alone. Every Condition carries a distinct icon as well as its colour and is named on its garage card — the in-race badge is icon-only but carries its name as an accessible label — your own row in the running order carries a red tick as well as full brightness, a car already chosen by another player is struck through as well as dimmed, and the difficulty levels are four bars filled to the level rather than four shades.
• Keyboard. Everything is a real <button>, the focus ring is visible on every surface, and a screen that is not showing is hidden outright rather than faded — so nothing invisible sits in the tab order. Setup makes the home screen behind it inert, and a pause or a result makes the instruments inert, so tabbing cannot walk out of the thing in front of you.
• Language. Every string in the interface is translated, including the reference pages, every setting and its description, and the aria-label on every icon-only control — pause, back, close, settings, and the two squares you spend.
• Touch. Every target is at least 40px on its short side, the two HUD squares are 56px, and the layout pads itself out of the safe-area insets on all four sides.
• Contrast. prefers-contrast: more firms up the hairlines, the secondary ink, the hover and selection washes and the glass — and High contrast in Settings applies the same treatment on demand, or turns it off. The palette does not change: black, white, grey and red, worked harder. forced-colors: active falls back to system colours with real borders.
• Desktop scaling. Menus use the full viewport and adapt their compositions to its width and height. The race retains its original portrait shell scaling and landscape layout, with a matching Canvas backing store.
• Orientation and resize. The world scales off the viewport height against a portrait phone as the reference, which is what keeps both orientations the same game: a short landscape viewport draws a smaller road and smaller cars, so the stretch of road in front of you, measured in car lengths, comes out identical. Below 480 points of height the standings panel tightens and the bottom row pulls in, on the page and in a split-screen column alike.

Browser support

Any current desktop or mobile browser. The game uses Canvas 2D, Pointer Events, Web Audio, the Gamepad API, matchMedia and localStorage, and degrades gracefully where newer features are missing — roundRect, ellipse, Path2D and canvas letterSpacing all have hand-written fallbacks, backdrop-filter has an opaque one, and a browser without inert simply keeps the older tab order.

Local play needs a device that reports (hover: hover) and (pointer: fine) — a computer — plus a controller per player.

Running it locally

There is nothing to install and nothing to build. Any static file server will do:

git clone https://github.com/hiyroscript/seren.git
cd seren
python3 -m http.server 8000
# then open http://localhost:8000

Opening index.html straight off the filesystem mostly works, but a server is better — some browsers restrict localStorage and canvas reads on file://.

To edit: change a file, reload the page. That is the whole loop.

Checking your changes

Because there is no build step, nothing normally catches a typo'd selector, a translation key that does not exist, or a second const with a name another file already used — the first two do nothing visible until you open the screen that uses them, and the third kills the page on load. One script finds all of it:

node tools/check.mjs
node tools/menu-check.mjs
node tools/ultimate-check.mjs
node tools/sprite-check.mjs
node tools/hitbox-check.mjs
node tools/dhaval-check.mjs

It is plain Node with no dependencies — there is no package.json and nothing to install — and it exits non-zero on failure, so it drops into a git hook or a CI job unchanged. It verifies:

• every stylesheet and script in index.html exists, is deferred, and is in the documented dependency order, with no inline <style> or <script> left behind
• every JavaScript file parses
• every top-level name is unique across all fifteen files, and none shadows a browser global
• every literal #id selector in the JavaScript resolves to an element that exists in index.html
• every string has all its languages, and every data-i18n attribute and literal t("…") call resolves to a string that exists
• every car has a draw branch, a name, an ultimate description, a button, a select-screen canvas; every Condition has a name, a description, a unique colour and one piece of icon artwork, and lands on the right Buff/Debuff page; no trace of the removed launch mechanic survives anywhere in the source or the page; every item has artwork and a valid rarity
• the Mystery Bubble reward gate is one named switch rather than a deletion, and the roll, the rarities, the artwork, oil, seekers and bubble rows all survive behind it
• Flann's ram, Neela's exchange, Lolanthe's aura, Verdant's invisibility and Rhosyn's Aero-Glow, Saffron's flight, Cole's form and Dhaval's aura use shared car predicates and measured per-car dimensions: flannCar(), neelaCar(), lolantheCar(), verdantCar(), rhosynCar(), saffronCar(), coleCar() and dhavalCar() are the only places a racer is compared to a car, the predicates built on them are read by the contact rules, the hazards, the bot mind, the inputs and the renderer, neelaFormActive() is still demonstrably narrower than neelaUltActive() (the alternate body, not the fifteen seconds), racerDetectable() is demonstrably a question about sight rather than about contact, Mind Control is set rather than added to anywhere in the source, the shared charge clock, duration and pace are untouched, every one of the five cars' own timings is a named constant in the tuning layer with the swap guard kept to a single step, only sprite cars carry a race scale and only within a measured band, and carHit() takes its hull and its size from the same model the sprite is drawn from
• Aero-Glow is a view over the canonical racer rather than a second race: no file writes an Aero-Glow value into G.biome, G.next, G.seam or G.trackT, no file keeps an Aero-Glow metre count, pose, origin or scroll beside the canonical one, the departure never reaches teleportRacerToPose() or rebaseWorld(), and reads — the one car-specific state it is allowed to know about, because it is the one that is about there being a body at all

Run it before you commit. It takes well under a second.

node tools/menu-check.mjs also checks menu state and event wiring using DOM/Canvas test doubles, including localization, every Settings preference and what it reaches, setup, simulated controllers, car turns and pause/results. node tools/ultimate-check.mjs runs the ultimate, Condition, hazard, contact and Mystery Bubble behaviour for all nine cars as player, bot and local seat, plus Neela's exchange, Lolanthe's aura and forced lane change and Verdant's directional defence in every ownership direction, the documented collision priority for every pair of ulting cars, the world-position regression that says moving player one leaves the rest of the road exactly where it was, and Aero-Glow's own invariants — the phase lifecycle, the canonical position and biome continuing through it, the isolation in both directions against every contact rule, hazard, pickup and targeting system, the two seconds of Invulnerable granted at the frame the car is genuinely back, finishing from inside it, pause, a forced wreck and a restart; node tools/sprite-check.mjs covers race sizes, all nine sprite cars' sheets and measured emitters, the ultimate fire, the transformation flash, Verdant's per-view opacity and Rhosyn's disappearance from every other view in one to four columns, and both note effects; node tools/hitbox-check.mjs covers contact geometry, including the switch between Neela's two measured hulls, Rhosyn's traced hull with the empty V between its nose prongs, and the invariant that hiding a Verdant or sending a Rhosyn away moves nothing. Browser visuals and hardware still need separate checks; see the redesign QA record, the ultimate record, the Flann record, the Neela record, the Lolanthe and Verdant record and the Rhosyn and Aero-Glow record.

Project layout

index.html          the document shell — screens, canvases, SVG icons, script tags
css/app.css         the entire stylesheet
v_flann.PNG         Flann’s image-backed vehicle, shared by menus and races
v_neela.PNG         Neela’s, likewise
vtm_neela.PNG       the shape Neela’s ultimate turns it into, races only
v_lolanthe.PNG      Lolanthe’s, likewise
v_verdant.PNG       Verdant’s, likewise
v_dhaval.PNG        Dhaval’s measured eighth-racer sprite
queen_note.PNG      the note that floats above an ulting Lolanthe, races only
pion_note.PNG       the three that orbit a Mind Controlled racer, races only
js/                 the game, in load order (see below)
tools/check.mjs     dependency-free validator for the invariants below
docs/               ARCHITECTURE.md, TUNING.md and the screenshots
upd                 the current brief
.nojekyll           tells GitHub Pages to serve the tree verbatim

The fifteen scripts load in a fixed, dependency-safe order with defer, so each may rely on the ones above it and nothing starts before every declaration exists.

File	Owns
core.js	storage with a memory fallback, the small maths/DOM helpers, capability flags
i18n.js	every string, the current language, and the sweep that writes them into the page
data.js	cars, difficulties, temperaments, conditions, items, tracks and every tuning constant
audio.js	the lazily-created Web Audio context, tones, noise, engine
runtime.js	canvas and context, road and split-view geometry, the game state object, layout/resize
ui.js	screen switching and focus gating, garage, custom setup, the car board, select-screen art
settings.js	every player preference, where it is stored, what applies it, and the Settings dialog
local.js	seats, player colours, pad discovery, the menu pad loops
ai.js	the bot mind: sense, weigh, act
mechanics.js	contact, lanes, boost, wrecks, Conditions, ultimates, items, hazards, particles
race.js	world seeding, the grid, the lifecycle, the finish, the per-frame update and frame loop
render.js	all Canvas 2D drawing
hud.js	the DOM HUD, the condition badges and their icons, the per-seat canvas HUD and the constants they share
input.js	keyboard, pointer and controller, translated into mechanics calls
main.js	boot: initial paints, event wiring, splash, settle

docs/ARCHITECTURE.md goes through how it fits together and where to change what. docs/TUNING.md is every dial in one place.

Deploying

It is a plain static site with relative asset paths, so it works under any base path. This repository is served by GitHub Pages from main — push, and the pages-build-deployment workflow republishes it. Any static host works the same way: copy index.html, the vehicle and effect .PNG files, css/ and js/ and you are done.

Known quirks

• Endless runs until you leave. The road contains your car and five racer bots, with hazards and items providing the obstacles.
• The internals are reachable from the console. The game runs as ordered classic scripts rather than inside a closure, so G, CARS, startUlt and the rest are global. Handy for debugging, and it means a determined player can poke the state. The only persisted value, the personal best, was always one localStorage.setItem away regardless.

Credit

A game by hiyroscript. No license file is present, so default copyright applies until the author adds one.

Shield presentation and contact feedback

Shield bars remain ordered pink → yellow → cyan, but lose durability cyan → yellow → pink. shieldBarFill() supplies both HUDs; SHIELD_GRADIENTS supplies matching borderless, dividerless gradient fills without changing bubble colors. SHIELD_MAX remains six halves. Respawn restores them after the existing wreck delay.

hitShield() preserves the current half count while ultOn is active. This neither regenerates shield nor grants universal invulnerability: surviving Obscured/Slow effects and car-specific solid-hazard behavior remain intact, and meteors still bypass durability under their existing destruction rules.

Accepted surviving hazard contacts refresh cosmetic shieldHitT to SHIELD_HIT_TIME (1 second). Frame updates count it down; wreck, respawn, finish and race reset clear it. shieldStage() selects the current color and half-state. drawShieldHit() shows one compact bar above the measured car silhouette, including the airborne render pass, suppresses the current viewport owner and uses the car's per-view alpha so invisible racers stay hidden. No-contact states and dodges produce no feedback. This timer has no gameplay effect.

Cole — car and motorcycle

Cole is the seventh racer. Tap the swap button beside the item holder, press Q, or press L1 / LB on a controller to change forms. Switching has a two-second simulation cooldown and works with items and ultimates disabled. It uses the shared transformation flash and preserves position, boost, ultimate time, and the chosen form through a wreck and the finish.

Form	Base pace	Boost multiplier	Ultimate multiplier
Car	1.0×	1.5×	2.0×
Motorcycle	1.5×	1.8×	2.3×

These multipliers stack with the ordinary pace effects. Cole’s ultimate clears tumbleweeds and meteors in either form; puddles and opponent attacks retain their usual behavior. Bots switch to the motorcycle after their opening reaction. A new race always begins in car form.

A full field has nine racers: local races with two, three, or four humans have seven, six, or five bots. See Cole measurements and QA. node tools/cole-check.mjs runs the focused integration checks; the ultimate suite includes them too.

Aureolin — armed car and turret

Aureolin is the ninth racer. Q, L1 / LB, or the vehicle-form button switches between the normal yellow camouflage car and its armed form with a two-second cooldown. Form survives a wreck; a new race starts normal.

While armed, hold Down / S, the right stick or D-pad down, or swipe down and keep the finger down to fire the turret. Each round adds an independently expiring 0.10× slowdown for 1.5 seconds. The yellow capacity bar sits below red boost, drains in 60 shots at 15 rounds/second, and recharges in 3.5 seconds. After overheating, it must reach 100% before another shot. The yellow bar also works with ordinary boost disabled.

The shared fifteen-second ultimate refills capacity, automatically fires the armed turret without drain, doubles newly fired bullet range from eight to sixteen normal Aureolin lengths, and automatically launches two homing rockets every two seconds when an opponent is ahead. Rockets continually seek the closest eligible racer ahead by race progress, last at most five seconds and remove one half-shield each on contact. The ultimate leaves form choice to the driver.

Flann’s ultimate absorbs shots; Verdant’s ultimate is revealed without damage or slowdown; Rhosyn’s ultimate is unreachable. Bullets miss flying Saffron, while rockets can follow it. Mind Control stops new firing; existing projectiles continue. Both Aureolin forms clear solid hazards during the ultimate; puddles still affect the car and projectiles pass over water.

See Aureolin measurements and QA. Run node tools/aureolin-check.mjs; the ultimate suite imports it as well.