-#define PI 3.14159265358979323846264338327
-#define PI_OVER_2 (PI / 2.0)
-#define PI3_OVER_2 ((3.0 * PI) / 2.0)
-#define PI_TIMES_2 (PI * 2.0)
-#define RADIANS_TO_DEGREES (180.0 / PI)
-#define DEGREES_TO_RADIANS (PI / 180.0)
+#define TAU 6.28318530717958647692528676655
+#define TAU_1QTR (TAU * 0.25)
+#define TAU_2QTR (TAU * 0.50)
+#define TAU_3QTR (TAU * 0.75)
+#define RADIANS_TO_DEGREES (360.0 / TAU)
+#define DEGREES_TO_RADIANS (TAU / 360.0)
+
+// Convenience definitions
+#define HALF_TAU (TAU_2QTR)
+#define QTR_TAU (TAU_1QTR)
+#define THREE_QTR_TAU (TAU_3QTR)