Code Forge: Python running in the browser, with 81 levels and spaced review
Code Forge is a platform for learning Python in depth: 9 chapters and 81 levels, each with a short lesson and a task checked by real tests. Python runs in the browser itself via WebAssembly (Pyodide), with no server, and what was learned comes back as spaced-review cards.
Client and context
Practice platforms usually need a server to run students' code, which is expensive and exposes infrastructure. And what is learned one day is gone the next week.
The problem
“I want to practice real Python, with tests, without installing anything and without forgetting it all a week later.”
Constraints
- No server to run code.
- Infinite loops cannot freeze the page.
- Progress saved with no account.
Decisions and trade-offs
Python in a Web Worker with Pyodide
Why: Real execution in the browser, no backend and no cost per student. A run longer than 15 seconds terminates the worker and a fresh runtime boots automatically.
YAML content validated against the real harness
Why: Every reference solution, starter and quiz runs against the real tests before publishing.
Spaced review (Leitner)
Why: Completed levels become cards returning after 1, 3, 7, 16, 35 and 80 days; skill measures what was recalled, not time spent.
What we built
- A Python track with 9 chapters and 81 levels, including a boss per chapter and a chapter on programming with AI.
- Monaco editor with tests run by Ctrl + Enter.
- Review cards, interleaved sessions, skills and rank based on what was recalled.
- Portuguese and English, light and dark themes.
Results
- 81levels in 9 chaptersSource: Live site
- 361automated tests across the track's exercisesSource: Repository content, Oct 13, 2026
- 0servers to run students' codeSource: Project architecture
This case's tile
Number of tests grading the exercises of each of the 9 Python track chapters.
| Automated tests per chapter | tests |
|---|---|
| Foundations | 34 |
| Functions and iteration | 38 |
| Classes and objects | 43 |
| Data structures | 30 |
| Files, data and tests | 40 |
| Advanced Python | 48 |
| Traps | 42 |
| Under the hood | 46 |
| Programming with AI | 40 |
Source: Code Forge content · 2026-10-13
Technologies
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