Thanks for your review, TPorter64.
I agree that sometimes the movement of the marbles is weird, because I used the Bullet plug-in to calculate movement. Physics plug-in is good, but it is better to sideview games. I think the Bullet plug-in is best to simulate physics in overview games.
I agree too that sometimes the CPU does not do a smart move. I am trying to fix this problem. Well, it is my first game in Construct 2!
I will try too give a better feedback in-game to avoid any confusion.