fix(styles): keep Snow wind sway bounded over time (#782)

The horizontal offset multiplied elapsed time by a sine, so flakes swung faster the longer the app ran. It is now the integral of the intended sway velocity, which stays bounded at any session age; Wind still scales the amplitude.

Co-authored-by: Sameh Khamis <[email protected]>

src/styles/snow.js

@@ -29,11 +29,13 @@ export const snowShader = {
       float depth = 0.5 + layer * 0.5;
       float speed = 0.4 + layer * 0.3;
       float size = mix(0.01, 0.025, layer);
-      float windForce = sin(time * 0.5 + layer * 3.14) * (0.05 + wind * 0.2);
+      float windForce = 0.05 + wind * 0.2;
 
       vec2 snowUV = uv * vec2(1.0, 0.5) * (4.0 + layer * 4.0);
       snowUV.y += time * speed;
-      snowUV.x += time * windForce;
+      // Offset is the integral of a swaying velocity sin(time * 0.5 + phase) * windForce,
+      // so the sway stays bounded however long the app has been running.
+      snowUV.x -= 2.0 * cos(time * 0.5 + layer * 3.14) * windForce;
 
       vec2 cell = floor(snowUV);
       vec2 f = fract(snowUV);