diff --git a/physics.c b/physics.c
index 5336df2..bc2eff3 100644
--- a/physics.c
+++ b/physics.c
@@ -1,5 +1,5 @@
 
-
+#include <unistd.h>
 #include "graphics.h"
 #include <stdlib.h>
 #include <string.h>
@@ -23,21 +23,14 @@ typedef struct Link {
 } Link;
 
 
-
-void draw_link(Canvas* c, Link* l){
-	line(c, l->a->x, l->a->y, l->b->x, l->b->y);
-}
-
-void update_point(Point* p){
-	uint tempx = p->x;
-	uint tempy = p->y;
-	p->x += (p->x - p->px) + p->fx;
-	p->y += (p->y - p->py) + p->fy;
-	p->px = tempx;
-	p->py = tempy;
-}
+void draw_link(Canvas* c, Link* l);
+void update_point(Point* p);
 
 
+
+/*
+ * main
+ */
 int main(){
 	char *data = malloc(40*40);
 	Canvas c = {40, 40, data};
@@ -64,9 +57,26 @@ int main(){
 		usleep(1000000/FRAMERATE);
 	}
 
-
-
 	return 0;
 }
 
+/*
+ * Draws a line between linked points
+ */
+void draw_link(Canvas* c, Link* l){
+	line(c, l->a->x, l->a->y, l->b->x, l->b->y);
+}
+
+/*
+ * Updates the position of a point
+ * the update is based on its position, its position in the previous frame (px, py) and the forces acting upon it (fx,fy)
+ */
+void update_point(Point* p){
+	uint tempx = p->x;
+	uint tempy = p->y;
+	p->x += (p->x - p->px) + p->fx;
+	p->y += (p->y - p->py) + p->fy;
+	p->px = tempx;
+	p->py = tempy;
+}