+Sprite * pixel_collides(float x, float y);
+void load_sprite(Sprite *sprite, char *filename);
+
+float sprite_mass(Sprite *s);
+void bounce(Sprite *a, Sprite *b);
+
+
+// extended sprites
+
+struct ship {
+ // core sprite fields
+ int8_t sprite_type;
+ int8_t flags;
+ struct ship *next;