I always get like 1 coin. I only got to lvl 2 once. But, I Have 104 coins. But, heres the glich. Voltorb always appears in the corner you start in. Unless, they have 0 voltorbs in that row.
http://pokemondb.net/pokebase/15164/is-there-an-easy-way-of-winning-the-voltorb-flip-minigame
