Easy data structure and algorithm practice puzzle.
Game menus are a stack: the pause menu sits on top of the game, and closing it returns you to exactly the game underneath. That makes the menu system a pushdown automaton, a state machine with a stack. A game starts on the "title" screen. Given a list of commands, either "push NAME" to open a screen on top or "pop" to close the top one, return the screens still open from bottom to top. The title screen can never be popped, since the game always needs something to show.
Solve it three ways: snap the jigsaw pieces together, fill in the blanks, or type it from scratch against the tests. This one is free.
Every line of the solution comes with a note explaining why it is there, and a step by step replay shows the code running. At level 3, where you type it yourself, you can ask for an AI mock interview on this problem that ends with a hiring manager's scorecard.
Then grow it into a real project with the Software Engineer button: this puzzle becomes the Entity Replay Log, a pipeline you can run and download. See every Software Engineer project.
Browse all 576 puzzles