How a simple 'dirty flag' stops Three.js games from overheating your phone

A developer noticed their phone getting uncomfortably hot while idling on a static Ludo board built with Three.js, a popular 3D web graphics library. The cause was the standard render loop taught in most tutorials, which instructs the GPU to redraw the entire scene 60 times per second regardless of whether anything on screen has changed. Switching to a simpler drawing method like Canvas2D would not have helped, since the problem lies in the loop logic, not the framework itself. The fix involves a 'dirty flag' — a simple true/false variable that is set to true only when something actually changes, so the GPU renders a new frame only when necessary. This small change kept the phone cool during idle moments while still allowing smooth animation whenever the scene actually updated.