It's an ok game
As it been said it's been done. But it's always quite fun to play it.
If I can make one recomendation is to challenge the player to do long series of bloon poping. This can be done by adding a multiplier. So every 30-50 bloons in a chain nets you more points. If the player misses one, the multiplier reset itself pretty standard stuff, but that sort of thing challenges the player. You could also record not only the longest chain, but also the longest distance travel.
Also as somedude294 said upgrades would be nice maybe something. That could help scare the crows away.