Lifelog: a personal operating system built with AI

▶ Live demo · fictitious data, runs entirely in your browser

Lifelog is the system I use every day to run a demanding routine: university, internship, technical studies and preparation for a language certification. It turns a weekly plan into a daily checklist and tracks progress with streaks, charts and checkpoints. Finances, calendar and study notebooks live in the same place.

I built it from scratch with AI, describing what I needed to Claude in natural language and evolving the app one feature at a time as my routine changed, up to the 14 modules shown here.

What it does

Module	What it is for
Dashboard	Progress ring for the day, streak, weekly focus time, latest mock-exam score, savings and today's priorities
Hoje (Today)	The day's checklist, generated from the weekly routine. Unfinished tasks roll over to the next day and priority tasks are marked
Rotina (Routine)	Weekly template editor. Some slots rotate topics automatically, e.g. a different SQL, ML or Cloud subject each week
Semana / Calendário	Week overview with time per area, plus a monthly calendar with notes
Certificação	Mock-exam log for 4 skills (Listening, Reading, Writing, Speaking), with trend chart and target line
Gráficos	Custom chart tabs (line, column, comparison, pie) fed by daily metrics
Flashcards	Spaced-repetition decks with grading (again / hard / good / easy)
Digitação	Rich-text notebooks and an error notebook (wrong → right → rule)
Checklists	Reusable, resettable checklists for exam day, essay review and the weekly review
Cadernos	Study notebooks per subject (SQL, Python, Statistics, ML, GenAI, Data Engineering, Cloud, BI) with links and review counters
Finanças	Monthly cycle (closes on a set day), fixed costs, expenses by category and savings
Foco	Pomodoro timer with alarm

AI features (in the real app)

In the private version, Lifelog runs as a Claude artifact and calls Claude from inside the app:

• Essay grading: scores a written text on 4 criteria, explains each score and lists what to improve.
• Inline writing correction: marks each mistake (grammar, spelling, collocation, word choice) and suggests the fix.
• Daily quote: picks a short, genuinely documented quote about discipline and perseverance.

These calls are disabled in the public demo, which has no AI backend.

Built-in logic worth noting

• Spaced repetition for study topics: completing a SQL, Python, ML or other study task schedules review tasks 1, 3, 7, 14 and 30 days later.
• Rollover and streaks: unfinished tasks move to the next day. A day counts toward the streak when its priority tasks are done.
• Day change detection: if the app stays open past midnight, it generates the new day without a reload.

Screenshots

Today	Certification tracking

Charts	Finances

Checklists	Mobile

How it was built

• AI-first development: every feature was specified in plain language and implemented with Claude, then tested and refined through iterations. Examples: "add a checklist tab", "make Python rotate one sub-topic per week", "don't lose the day if the page stays open overnight".
• Runtime: a single self-contained HTML/CSS/JavaScript file running as a Claude artifact, with a document database (Firestore-style API: collections, documents, where/orderBy queries).
• No framework: vanilla JS, hand-made SVG charts, responsive layout (sidebar on desktop, bottom tab bar on mobile).

About this demo

• The app code is the same as the real Lifelog. Only the runtime is swapped: a small shim at the top of index.html re-implements the database API on top of localStorage, so it runs on GitHub Pages.
• All data is fictitious and generated on your first visit: tasks for the last two weeks, mock exams, metrics, expenses and calendar notes. Nothing is sent anywhere.
• To start over, open the browser console and run lifelogDemoReset().
• AI features and file uploads are disabled, since they need the Claude runtime.

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Author: Caio Bandeira · LinkedIn · GitHub