fix: calculate beat_phase for FlashEffect and refactor uniforms

- seq_compiler.py: Calculate beat_phase from beat_time (was hardcoded 0.0f)
- Refactor: Replace CommonPostProcessUniforms with UniformsSequenceParams
- Remove duplicate struct definition in post_process_helper.h
- Update all CNN effects and tests to use unified uniform struct
- Fixes FlashEffect showing solid white instead of flashing to beat

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

3 files changed, 9 insertions, 7 deletions

diff --git a/tools/cnn_test.cc b/tools/cnn_test.cc
index d88956d..a209cdf 100644
--- a/tools/cnn_test.cc
+++ b/tools/cnn_test.cc
@@ -1332,7 +1332,7 @@ int main(int argc, char** argv) {
   // Create uniform buffers
   const WGPUBufferDescriptor common_uniform_desc = {
       .usage = WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst,
-      .size = sizeof(CommonPostProcessUniforms),
+      .size = sizeof(UniformsSequenceParams),
   };
   WGPUBuffer common_uniform_buffer =
       wgpuDeviceCreateBuffer(device, &common_uniform_desc);
@@ -1384,7 +1384,7 @@ int main(int argc, char** argv) {
     printf("Processing layer %d/%d...\n", layer + 1, NUM_LAYERS);
 
     // Update uniforms
-    CommonPostProcessUniforms common_u = {
+    UniformsSequenceParams common_u = {
         .resolution = {static_cast<float>(width), static_cast<float>(height)},
         .aspect_ratio = static_cast<float>(width) / static_cast<float>(height),
         .time = 0.0f,
@@ -1410,7 +1410,7 @@ int main(int argc, char** argv) {
         BindGroupBuilder()
             .sampler(0, sampler)
             .texture(1, current_input)
-            .buffer(2, common_uniform_buffer, sizeof(CommonPostProcessUniforms))
+            .buffer(2, common_uniform_buffer, sizeof(UniformsSequenceParams))
             .buffer(3, layer_params_buffer, sizeof(CNNv1LayerParams))
             .texture(4, original_view)
             .build(device, bgl);
diff --git a/tools/seq_compiler.py b/tools/seq_compiler.py
index 6b72ebd..3b8d126 100755
--- a/tools/seq_compiler.py
+++ b/tools/seq_compiler.py
@@ -516,7 +516,8 @@ void RenderTimeline(WGPUCommandEncoder encoder, float time, int width, int heigh
                       float beat_time, float audio_intensity) {
     Sequence* seq = GetActiveSequence(time);
     if (seq) {
-        seq->preprocess(time, beat_time, 0.0f, audio_intensity);
+        float beat_phase = fmodf(beat_time, 1.0f);
+        seq->preprocess(time, beat_time, beat_phase, audio_intensity);
         seq->render_effects(encoder);
     }
 }
@@ -584,7 +585,8 @@ void RenderTimeline(WGPUSurface surface, float time, int width, int height,
     seq->set_sink_view(g_sink_view);
 
     // Update uniforms via preprocess
-    seq->preprocess(time, beat_time, 0.0f, audio_intensity);
+    float beat_phase = fmodf(beat_time, 1.0f);
+    seq->preprocess(time, beat_time, beat_phase, audio_intensity);
 
     WGPUCommandEncoder encoder = wgpuDeviceCreateCommandEncoder(ctx->device, nullptr);
 
diff --git a/tools/shadertoy/template.cc b/tools/shadertoy/template.cc
index 7636c0a..56b4ab5 100644
--- a/tools/shadertoy/template.cc
+++ b/tools/shadertoy/template.cc
@@ -83,7 +83,7 @@ void ShaderToyEffect::init(MainSequence* demo) {
       {.binding = 1, .textureView = prev_view},
       {.binding = 2,
        .buffer = uniforms_.get().buffer,
-       .size = sizeof(CommonPostProcessUniforms)},
+       .size = sizeof(UniformsSequenceParams)},
       {.binding = 3,
        .buffer = params_.get().buffer,
        .size = sizeof(ShaderToyParams)},
@@ -98,7 +98,7 @@ void ShaderToyEffect::init(MainSequence* demo) {
 
 void ShaderToyEffect::render(WGPURenderPassEncoder pass, float time, float beat,
                              float intensity, float aspect_ratio) {
-  const CommonPostProcessUniforms uniforms = {
+  const UniformsSequenceParams uniforms = {
       .resolution = {static_cast<float>(width_), static_cast<float>(height_)},
       .aspect_ratio = aspect_ratio,
       .time = time,