diff --git a/a8/collision.cc b/a8/collision.cc
index 07ed6f0..636314c 100644
--- a/a8/collision.cc
+++ b/a8/collision.cc
@@ -244,9 +244,9 @@ namespace a8
         return false;
     }
 
-    bool CircleContainCircle(a8::Vec2 a_pos, float a_rad, a8::Vec2 b_pos, float b_rad)
+    bool CircleContainCircle(glm::vec2 a_pos, float a_rad, glm::vec2 b_pos, float b_rad)
     {
-        float distance = (a_pos - b_pos).Norm();
+        float distance = glm::length(a_pos - b_pos);
         return distance < a_rad - b_rad;
     }
 
diff --git a/a8/collision.h b/a8/collision.h
index 133b19e..ac5a81f 100644
--- a/a8/collision.h
+++ b/a8/collision.h
@@ -28,7 +28,7 @@ namespace a8
                             float b_height);
     bool IntersectSectorCircle(a8::Vec2 a_pos, float angle, float a_rad, a8::Vec2 b_pos, float b_rad);
     bool IntersectSectorAabb(a8::Vec2 a_pos, float angle, float a_rad, a8::Vec2 b_min, a8::Vec2 b_max);
-    bool CircleContainCircle(a8::Vec2 a_pos, float a_rad, a8::Vec2 b_pos, float b_rad);
+    bool CircleContainCircle(glm::vec2 a_pos, float a_rad, glm::vec2 b_pos, float b_rad);
     bool CalcCircleAabbSafePoint(a8::Vec2 a_pos, float a_rad, a8::Vec2 b_min, a8::Vec2 b_max,
                                  a8::Vec2& new_pos);
     bool CalcCircleCircleSafePoint(a8::Vec2 a_pos, float a_rad, a8::Vec2 b_pos, float b_rad,