Not that I endorse it, but you could do some (or all) of the following to preserve the suggested system while still having everyone's favorite size of transactions:

- Ads after X failures

- Spend Fun Points to avoid ads and prevent misclicks from subtracting your score

- Fun points can be bought

- or obtained by watching an ad

- or obtained very rarely through regular play (e.g. by spending many Fun Coins)

- Spend Fun Coins to customize your ball and background

- Fun coins can be bought

- or obtained by watching an ad

- or obtained infrequently through regular play

- Daily bonuses which scale with number of consecutive days logged in

- Fun Points and/or Coins obtained by referring a friend

et cetera