Why the Restart Button Is the Ultimate Test for Hidden Game State Bugs

In browser game development, the restart button often exposes hidden state bugs that normal gameplay does not reveal. A proper restart must reset all game elements — including player stats, enemy timers, active projectiles, and event listeners — not just visible components like the score. A common mistake is storing game objects in module-level variables and spawning a new animation loop on each restart, which causes issues like doubled collision detection and faster movement after multiple restarts. Developers are advised to implement a simple state machine that fully tears down the current run before initializing a new one, ensuring each run owns its own entities and callbacks. Repeatedly cycling through start, lose, and restart sequences is recommended as a reliable way to catch duplicated listeners and stale references.