1 files changed, 43 insertions, 0 deletions
diff --git a/collision.cpp b/collision.cpp
new file mode 100644
index 0000000..1ffe957
--- /dev/null
+++ b/collision.cpp
@@ -0,0 +1,43 @@
+#include "balls.h"
+
+static double clamp(double v, double lo, double hi);
+static double min(double a, double b);
+static double max(double a, double b);
+
+int
+isCollision(Point p1, double r1, Point p2, double r2) {
+	double dx, dy;
+
+	dx = p1.x - p2.x;
+	dy = p1.y - p2.y;
+	return (dx*dx + dy*dy) <= (r1+r2)*(r1+r2);
+}
+
+void
+collideWall(Ball *b, Rectangle wall) {
+	wall = insetRect(wall, b->r);
+
+	if (b->p.x < wall.min.x || b->p.x > wall.max.x) {
+		b->p.x = clamp(b->p.x, wall.min.x, wall.max.x);
+		b->v.x = -b->v.x;
+	}
+	if (b->p.y < wall.min.y || b->p.y > wall.max.y) {
+		b->p.y = clamp(b->p.y, wall.min.y, wall.max.y);
+		b->v.y = -b->v.y;
+	}
+}
+
+static double
+clamp(double v, double lo, double hi) {
+	return min(hi, max(v, lo));
+}
+
+static double
+min(double a, double b) {
+	return (a < b) ? a : b;
+}
+
+static double
+max(double a, double b) {
+	return (a > b) ? a : b;
+}