From dc96fcd771bea09d726a760266739906e95c09a6 Mon Sep 17 00:00:00 2001
From: Vasco <true.vasco.alves@gmail.com>
Date: Sun, 23 Aug 2026 02:25:33 +0100
Subject: Peak 0.1.1

---
 Fuse/fuse_tween.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 Fuse/fuse_tween.c

(limited to 'Fuse/fuse_tween.c')

diff --git a/Fuse/fuse_tween.c b/Fuse/fuse_tween.c
new file mode 100644
index 0000000..2b47f41
--- /dev/null
+++ b/Fuse/fuse_tween.c
@@ -0,0 +1,68 @@
+#pragma once
+
+#include "fuse.h"
+#include "fuse_internal.h"
+
+static inline float
+fuse__get_coef(FuseAnimation anim, float t)
+{
+    switch (anim) {
+        case FUSE_ANIMATION_EASE_IN:  return t * t;
+        case FUSE_ANIMATION_EASE_OUT: return t * (2.0f - t);
+        case FUSE_ANIMATION_LINEAR:   
+        default:                      return t;
+    }
+}
+
+static inline float
+fuse__ping_pong(float duration_sec, uint64_t time_ns)
+{
+    if (duration_sec <= 0.0f) return 1.0f;
+    
+    uint64_t duration_ns = (uint64_t)(duration_sec * 1000000000.0f);
+    
+    // modulo against DOUBLE the duration to handle reversing
+    uint64_t loop_time_ns = time_ns % (duration_ns * 2);
+    
+    // in the second half REVERSE the clock direction
+    if (loop_time_ns > duration_ns) {
+        loop_time_ns = (duration_ns * 2) - loop_time_ns;
+    }
+    
+    return (float)loop_time_ns / (float)duration_ns;   
+}
+
+extern float
+fuse_tween_f(FuseAnimation anim, float f1, float f2, float duration, uint64_t time_ns)
+{
+    float t = fuse__ping_pong(duration, time_ns);
+    float coef = fuse__get_coef(anim, t);
+    return f1 + coef * (f2 - f1);
+}
+
+extern int
+fuse_tween_i(FuseAnimation anim, int i1, int i2, float duration, uint64_t time_ns)
+{
+    float t = fuse__ping_pong(duration, time_ns);
+    float coef = fuse__get_coef(anim, t);
+    return (int)(i1 + coef * (i2 - i1));
+}
+
+extern uint32_t
+fuse_tween_color(FuseAnimation anim, uint32_t c1, uint32_t c2, float duration, uint64_t time_ns)
+{
+    float t = fuse__ping_pong(duration, time_ns);
+    float coef = fuse__get_coef(anim, t);
+
+    int r1 = (c1 >> 24) & 0xFF, r2 = (c2 >> 24) & 0xFF;
+    int g1 = (c1 >> 16) & 0xFF, g2 = (c2 >> 16) & 0xFF;
+    int b1 = (c1 >> 8)  & 0xFF, b2 = (c2 >> 8)  & 0xFF;
+    int a1 =  c1        & 0xFF, a2 =  c2        & 0xFF;
+
+    uint32_t r = (uint32_t)(r1 + coef * (r2 - r1));
+    uint32_t g = (uint32_t)(g1 + coef * (g2 - g1));
+    uint32_t b = (uint32_t)(b1 + coef * (b2 - b1));
+    uint32_t a = (uint32_t)(a1 + coef * (a2 - a1));
+
+    return (r << 24) | (g << 16) | (b << 8) | a;
+}
-- 
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