diff --git a/src/collision.h b/src/collision.h
index 7e1a953..5e4b9db 100644
--- a/src/collision.h
+++ b/src/collision.h
@@ -2,17 +2,19 @@
 #define _fencer_collision_h
 
 #include "shape.h"
+#include "physics_entity.h"
 #include <stddef.h>
 
-struct Collision {
-    Shape* other;
-
+typedef struct Collision {
+    PhysicsEntity other;
     Vector point;
     Vector normal;
     Vector velocity;
-
+    Vector separation_force;
     size_t edge_left;
     size_t edge_right;
-};
+} Collision;
+
+extern Collision get_collision(PhysicsEntity a, PhysicsEntity b);
 
 #endif // !_fencer_collision_h