diff --git a/bin/Makefile b/bin/Makefile
index 1416a00..77808b5 100644
--- a/bin/Makefile
+++ b/bin/Makefile
@@ -16,7 +16,7 @@ CTTF = `freetype-config --cflags`
 CGL  =
 CFLAGS = -Wall $(CLUA) $(CSDL) $(CXML) $(CTTF) $(CGL) $(VERSION)
 ifdef DEBUG
-CFLAGS += -g3 -DDEBUG
+CFLAGS += -g3 -DDEBUG -DLUA_USE_APICHECK
 else
 CFLAGS += -O2
 endif
diff --git a/src/physics.h b/src/physics.h
index ec0645c..a674dfb 100644
--- a/src/physics.h
+++ b/src/physics.h
@@ -1,8 +1,8 @@
 #pragma once
 #include "def.h"
 
-#define VX(v)     ((v).mod*cos((v).angle))
-#define VY(v)     ((v).mod*sin((v).angle))
+#define VX(v)     ((v).x)
+#define VY(v)     ((v).y)
 #define VMOD(v)   ((v).mod)
 #define VANGLE(v) ((v).angle)
 
@@ -11,7 +11,8 @@
 
 // Base of 2D vectors.
 typedef struct {
-  double mod, angle; // Basic 2D vector components.
+  double x, y; // Cartesian values.
+  double mod, angle; // Polar values.
 } Vec2;
 
 // Vector manupulation.