src/examples/2048.c

@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <math.h>
 
 #define SIZE 4
 #define MOVE_DURATION 0.12f
@@ -74,6 +75,42 @@ colors(uint32_t number)
     }
 }
 
+/* Maps positive values logarithmically: powers of two get evenly spaced hues.
+   Returns 0xRRGGBB. Values outside [min_value, max_value] are clamped. */
+uint32_t
+color_for_value(double value, double min_value, double max_value)
+{
+    if (min_value <= 0.0 || max_value <= min_value || value <= 0.0)
+        return 0xFFFFFF;
+
+    if (value < min_value) value = min_value;
+    if (value > max_value) value = max_value;
+
+    double t = (log2(value) - log2(min_value)) /
+               (log2(max_value) - log2(min_value));
+    
+    t = sqrt(t);  /* accelerates color changes near the low end */
+
+    /* Sweep hue from blue to red in HSV; full saturation and brightness. */
+    // double h = (1.0 - t) * 240.0;
+
+    double exponent = log2(value / min_value);  /* 0 at min_value, 1 per doubling */
+    double h = fmod(20.0 + exponent * 45.0, 360.0);
+
+    double c = 1.0;
+    double x = 1.0 - fabs(fmod(h / 60.0, 2.0) - 1.0);
+    double r, g, b;
+
+    if      (h < 60.0)  { r = c; g = x; b = 0.0; }
+    else if (h < 120.0) { r = x; g = c; b = 0.0; }
+    else if (h < 180.0) { r = 0.0; g = c; b = x; }
+    else                { r = 0.0; g = x; b = c; }
+
+    return ((uint32_t)(r * 255.0) << 16) |
+           ((uint32_t)(g * 255.0) << 8)  |
+            (uint32_t)(b * 255.0);
+}
+
 /*
  * Return the board coordinate for position p in a line, where p=0 is
  * the side toward which tiles move.
@@ -323,7 +360,7 @@ draw_tile_rect(uint32_t value, float x, float y, float w, float h)
     uint32_t iy = (uint32_t)y;
     uint32_t iw = (uint32_t)w;
     uint32_t ih = (uint32_t)h;
-    uint32_t color = colors(value);
+    uint32_t color = color_for_value((double)value, 2, 131072);
 
     put_rect(OVERDRAW, ix, iy, iw, ih, color);
 

src/examples/CMakeLists.txt

@@ -3,6 +3,7 @@
 
 add_executable(game_2048 2048.c)
 target_link_libraries(game_2048 PRIVATE dangerzone_engine)
+target_link_libraries(game_2048 PRIVATE m)
 
 #add_executable(game_window window.c)
 #target_link_libraries(game_window PRIVATE dangerzone_engine)