3 files changed, 29 insertions, 23 deletions
diff --git a/src/shaders/debug/debug_print.wgsl b/src/shaders/debug/debug_print.wgsl
index 22b5838..7e6debe 100644
--- a/src/shaders/debug/debug_print.wgsl
+++ b/src/shaders/debug/debug_print.wgsl
@@ -11,6 +11,8 @@
 //                    each component holds 4 chars (MSB = leftmost char)
 //                    e.g. "Hi!" -> vec4u(0x48692100u, 0u, 0u, 0u), 3u
 
+const ink_color = vec4f(1.0, 1.0, 0.0, 1.0);  // yellow
+
 // Returns lit pixel (0 or 1) for ASCII code [0x20-0x7E], row r [0-7], col c [0-7].
 // Encoding: 2 u32s per glyph; hi covers rows 0-3, lo covers rows 4-7.
 // Within each u32, row r occupies bits [(3-r%4)*8+7 : (3-r%4)*8].
@@ -217,8 +219,7 @@ fn _dbg_char(ascii: u32, r: u32, c: u32) -> u32 {
 // pixel_pos : @builtin(position).xy
 // origin    : top-left corner of text in screen pixels
 // value     : f32 to display  (format: [-]DDD.DDD, 64×8 px)
-fn debug_f32(col: vec3f, pixel_pos: vec2f, origin: vec2f, value: f32) -> vec3f {
-    let ink_color = vec3f(1.0, 1.0, 0.0);  // yellow
+fn debug_f32(col: vec4f, pixel_pos: vec2f, origin: vec2f, value: f32) -> vec4f {
     let lp = pixel_pos - origin;
     if (lp.x < 0.0 || lp.x >= 64.0 || lp.y < 0.0 || lp.y >= 8.0) {
         return col;
@@ -256,8 +257,8 @@ fn debug_f32(col: vec3f, pixel_pos: vec2f, origin: vec2f, value: f32) -> vec3f {
 //
 // Example — "Hello" (5 chars, ASCII 0x48 0x65 0x6C 0x6C 0x6F):
 //   debug_str(col, pos.xy, origin, vec4u(0x48656C6Cu, 0x6F000000u, 0u, 0u), 5u)
-fn debug_str(col: vec3f, pixel_pos: vec2f, origin: vec2f, s: vec4u, len: u32) -> vec3f {
-    let ink_color = vec3f(1.0, 1.0, 0.0);  // yellow
+fn debug_str(col: vec4f, pixel_pos: vec2f, origin: vec2f, s: vec4u, len: u32) ->
+vec4f {
     let lp = pixel_pos - origin;
     let max_w = f32(len * 8u);
     if (lp.x < 0.0 || lp.x >= max_w || lp.y < 0.0 || lp.y >= 8.0) {
diff --git a/src/shaders/math/noise.wgsl b/src/shaders/math/noise.wgsl
index dd97e02..dff6619 100644
--- a/src/shaders/math/noise.wgsl
+++ b/src/shaders/math/noise.wgsl
@@ -21,6 +21,13 @@ fn hash_2f(p: vec2f) -> f32 {
   return fract(sin(h) * 43758.5453123);
 }
 
+// variant for vec2f -> f32 hashing
+fn hash_2f_alt(p: vec2f) -> f32 {
+  var p3  = fract(p.xyx * .1376);
+  p3 += dot(p3, p3.yzx + 33.33);
+  return fract((p3.x + p3.y) * p3.z);
+}
+
 // Hash: vec2f -> vec2f
 // 2D coordinate to 2D hash (from Shadertoy 4djSRW)
 fn hash_2f_2f(p: vec2f) -> vec2f {
diff --git a/src/shaders/render/scratch_lines.wgsl b/src/shaders/render/scratch_lines.wgsl
index 04ed6f8..6123486 100644
--- a/src/shaders/render/scratch_lines.wgsl
+++ b/src/shaders/render/scratch_lines.wgsl
@@ -12,24 +12,22 @@
 #include "math/noise"
 
 fn scratch_lines(uv: vec2f, resolution: vec2f, time: f32) -> f32 {
-    // Quantize to ~24fps to simulate film frame rate
-    let t = floor(time * 24.0);
+  // Quantize to ~24fps to simulate film frame rate
+  let t = floor(time * 24.0);
 
-    var intensity = 0.0;
-    for (var i = 0; i < 8; i++) {
-        let seed = f32(i) * 17.3 + t;
-        // ~25% chance this scratch is visible this frame
-        let visible = step(0.75, hash_1f(seed + 3.1));
-        // Random vertical position [0, 1]
-        let y = hash_1f(seed + 7.9);
-        // Thickness in pixels [1, 4]
-        let thickness = hash_1f(seed + 13.5) * 3.0 + 1.0;
-        // Brightness [0.5, 1.0]
-        let brightness = hash_1f(seed + 21.7) * 0.5 + 0.5;
-        // Soft linear falloff from line center
-        let dy = abs(uv.y - y) * resolution.y;
-        let line = clamp(1.0 - dy / thickness, 0.0, 1.0);
-        intensity += line * brightness * visible;
-    }
-    return clamp(intensity, 0.0, 1.0);
+  // Scanlines
+  let scan = abs(sin(uv.y * uniforms.resolution.y * 3.14159265));
+  var intensity = 0.2 * scan;
+
+  // Per-pixel temporal noise
+  let pixel = floor(uv * uniforms.resolution * .4);
+  let n = hash_2f(pixel + vec2f(time * 47.3, time * 31.7)) * 0.04 - 0.02;
+  intensity += n;
+
+  // Horizontal jitter line (random scanline rolling artifact)
+  let jitter_y = hash_1f(fract(t * 0.37));
+  let jitter_band = abs(uv.y - jitter_y);
+  let scratch = smoothstep(5. / uniforms.resolution.y, 0., jitter_band);
+  intensity += scratch * 0.11 * hash_1f(uv.x * 100.0 + t);
+  return clamp(intensity, 0.0, 1.0);
 }