After a while, I was finally able to create what I've been wanting to--a REAL gravity simulation. (I have to give some credit to boisvert, because it was his code that supplied me with that tiny extra bit of information I needed to make this work.) To demonstrate this is original, I've made it so that you can move the "gravity" icon--sure enough, the marble will react appropriately. ARROW KEYS-- move "Gravity" around. D-- pen down (also generates random color). U-- pen up. C-- clear. Have fun!! XD