Quick answer: Construct 3 game losing touch tracking after fullscreen toggle? Browser fires pointercancel on the transition - listen for it and re-register active touches.
Player taps fullscreen during gameplay. Their finger was already on the screen for movement; movement stops.
Listen for pointercancel
On the system event, treat as 'released'. Update gameplay state as if the player lifted their finger. Less surprising than a stuck movement state.
Or capture pointer
pointerCapture in JS keeps the pointer reference even across fullscreen. More complex; works.
Disable fullscreen mid-game
For mobile-first games, hide the fullscreen toggle during active play. Surface it only on menus where the state change is recoverable.
“Fullscreen is a browser-level transition. Game state has to know.”
Test the toggle in every state your game has. The bug class hides in transitions you didn't think about.