im going to say the same as i say on other td games... On the final wave sell the towers most units are finished going to (if you are confident) and use the money to build even new towers where units are comming, its a bit more complicated because there is a chance of the unit to come back... Its your decision.
Tip: On the final or last wave sell the towers that dont have units incomming. Although you get less gold you can still use the gold from the towers for the units in front!
my strategy is to stay low and im getting $1000 per turn. The bonuses at the bottom will keep you bouncing up and you can use the fuel to guide you up if your about to go on the ground. I reccomend you to use this tactic.
The game is great! but I would change the achievement list, I would like it if the list of achievements or quests could all be on a long list. I achieved some of these things before and now I have to do them again. Not a need but a want. 100/100 :3
bad trainers... my swimming trainer tried feeding me to the crocs... the flying one made me impact into pieces of rock.... my climbing one let avalanches fall on me!