CheckiO
Solve Python or TypeScript missions and compare your code with others
CheckiO gives you coding missions to solve in Python or TypeScript. You write a solution in the browser, check it against tests, and open up new missions on a game map. After you solve a mission, you can read and discuss other players' solutions, which is often where you learn the most.
Free · No login · Browser · Intermediate
About CheckiO
When you start a game, you pick Easy, Normal or Advanced, which changes how missions are laid out on the map. It suits beginners who know the basics and experienced coders who want cleaner code. Teachers can use classrooms to follow students' progress.
It runs in the browser. You can start without registering, and free accounts exist with some limits.
On Breakpoint since 23 Oct 2026.