Learn to code with an AI you can interrupt

Pick an exercise. Write it yourself, or watch the AI draft a solution and stop it the moment you want to take over. Everything runs in your browser and is checked against real tests.

✓ AI writes while you watch✓ Stop it and take over anytime✓ Runs in your browser

Python

CPython 3.12 compiled to WebAssembly. Runs in your browser, not on our servers.

Beginner

Variables, loops, strings, conditionals. One idea per exercise.

12 exercises · ~83 min

Intermediate

Comprehensions, classes, generators, sorting, recursion.

12 exercises · ~134 min

Advanced

Dynamic programming, graphs, protocols, caches, rate limiting.

12 exercises · ~202 min

JavaScript

Runs natively in an isolated worker. Nothing to download.

Beginner

Variables, loops, strings, conditionals. One idea per exercise.

2 exercises · ~10 min

Intermediate

Comprehensions, classes, generators, sorting, recursion.

2 exercises · ~20 min

Advanced

Dynamic programming, graphs, protocols, caches, rate limiting.

2 exercises · ~38 min

SQL

Query a ready-made shop database. SQLite runs in your browser - unlimited and free.

Beginner

Variables, loops, strings, conditionals. One idea per exercise.

3 exercises · ~18 min

Intermediate

Comprehensions, classes, generators, sorting, recursion.

3 exercises · ~28 min

Advanced

Dynamic programming, graphs, protocols, caches, rate limiting.

3 exercises · ~40 min

C

Compiled with gcc in a locked-down sandbox on our server.

Beginner

Variables, loops, strings, conditionals. One idea per exercise.

2 exercises · ~16 min

Intermediate

Comprehensions, classes, generators, sorting, recursion.

2 exercises · ~20 min

Advanced

Dynamic programming, graphs, protocols, caches, rate limiting.

2 exercises · ~26 min

C++

Compiled with g++ (C++17) in a locked-down sandbox on our server.

Beginner

Variables, loops, strings, conditionals. One idea per exercise.

2 exercises · ~16 min

Intermediate

Comprehensions, classes, generators, sorting, recursion.

2 exercises · ~22 min

Advanced

Dynamic programming, graphs, protocols, caches, rate limiting.

2 exercises · ~26 min

Java

Compiled and run on OpenJDK 17 in a locked-down sandbox on our server.

Beginner

Variables, loops, strings, conditionals. One idea per exercise.

2 exercises · ~15 min

Intermediate

Comprehensions, classes, generators, sorting, recursion.

2 exercises · ~20 min

Advanced

Dynamic programming, graphs, protocols, caches, rate limiting.

2 exercises · ~24 min

C#

Compiled with Mono in a locked-down sandbox on our server.

Beginner

Variables, loops, strings, conditionals. One idea per exercise.

2 exercises · ~15 min

Intermediate

Comprehensions, classes, generators, sorting, recursion.

2 exercises · ~19 min

Advanced

Dynamic programming, graphs, protocols, caches, rate limiting.

2 exercises · ~24 min

How it works

1. Read the brief — Every exercise says exactly what to build, including the edge cases.
2. Write it, or let the AI start — Press Let AI write it and the solution appears line by line in the editor.
3. Stop whenever you like — The code written so far stays and is yours to edit. Finishing a half-written function teaches more than reading a whole one.
4. Run it — Your code runs in this browser and is checked against the exercise tests. Nothing is sent anywhere to be executed.