Cache static background layers in Canvas games
The practical problem
A grid puzzle redraws the same tiles and star fields every frame even though only the beam moves. This burns CPU and creates unnecessary draw operations.
Implementation protocol
Pre-render stable geometry onto an offscreen surface, then composite it. Separate mutable effects from immutable décor and minimize repeated shadowBlur and canvas state changes.
Worked scenario
A 7×7 board needs only a one-time draw of static tile borders, with each frame updating the moving laser and selection state. Measure render CPU time before caching.
What could go wrong
Caching a huge full-screen backing surface can increase RAM and create GPU upload costs.
Acceptance criteria
Test low-memory devices and free caches when a scene changes.
Source material and evidence boundaries
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