TapDefense is a good free tower defense game for iDevice.
This game is a little bit unusual in the genre. It has the "interest rate" concept that awards you gold based on your current gold, even if you lose the round. And that is important to know.
So, to beat this game, follow these steps:
- Save money! SAVE MONEY! Seriously, if you can get through one round without spending and with few missed creeps, do it. You earn more money even if you do not fully clear the round. And the interest earns you so much more money if your pot is already big.
- Put all your first few "halo" to increase your interest rate. You should do this until you reach about 20% interest (about level 16, I think).
- Research only ice and storm. Ice should be researched first, then storm on later rounds.
- Spread your storm towers out. You probably only need four of them.
- Mingle ice towers in between storms. You'll need this so that the storm tower can target different creeps, instead of always aiming for the same guy.
- Finish off the creeps with canon towers.
- Initially, build one or two cannons, one or two waters, and maybe just one arrow.
- Upgrade towers to the max. Upgraded towers are so much better than two, or three towers combined.