glslViewer's `u_mouse` is in pixels, not 0..1 — normalize by `u_resolution` before use

glslViewer reports u_mouse in pixel coordinates, not the normalized 0..1 range beginners often assume. To use it as a fractional position, divide by resolution: u_mouse/u_resolution. Shadertoy’s iMouse is also in pixels, but additionally carries click-state in its .zw components — glslViewer has no equivalent, so .zw must be dropped when porting. Using u_mouse unnormalized places interaction far off-screen or in one corner.

Examples

vec2 m = u_mouse / u_resolution; // normalized 0..1 float d = length(uv - u_mouse); // wrong: mixes pixel and normalized coords

Assessment

A shader positions a circle at u_mouse but it only appears in the far corner. Explain the coordinate mismatch and write the corrected expression.