kik shader: derive step from resolution so the full preview scales

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -20,6 +20,10 @@ Shaders define `mainImage(out vec4 fragColor, in vec2 fragCoord)` and may
 use `iResolution`, `iTime`, `iTimeDelta` and `iFrame`. The file is reloaded
 when it changes; on a compile error the last working shader keeps running.
 
+The same shader also runs at full size in the debug window, so derive the
+step from the resolution (`floor(fragCoord.x / iResolution.x * 16.0)`) or use
+`fragCoord.x / iResolution.x`, never raw `fragCoord.x`.
+
 White channel: `extract` (default) sets `w = min(r,g,b)` and subtracts it
 from rgb, `alpha` uses the shader's alpha, `off` sends w = 0.
 

shaders/kik.glsl

@@ -150,7 +150,7 @@ vec3 events(vec3 col, float i, float t) {
 }
 
 void mainImage(out vec4 fragColor, in vec2 fragCoord) {
-    float i = floor(fragCoord.x);
+    float i = floor(fragCoord.x / iResolution.x * 16.0);  // step, also in the big preview
     float t = iTime;
 
     float k = floor(t / SCENE_LEN);