A tip for Run'N'Gun mode: The bats don't attack you so long as you're in the night time sequence and you have a little rainbow following you. As a result you can stack up a pretty good number of bats for some hot combos as long as you don't take any damage (get run into by a dinosaur thing or jump/run into a bat). Wait until the night time sequence is coming to an end and then unleash on the gathered up bats.
There's one thing however, you have to get a pretty decent combo going in the first place to activate it (4 in a row maybe?).
Good luck and have fun!
The music was excellent and I very much enjoyed the game concept.
The interface responsiveness was a bit frustrating at times but that is my only detracting comment.
I agree with Chris, for the fourth level spam Assault units and Riflemen and then just throw as many grenades at the tanks as you can until they blow up.
Later on if you're playing levels where you can build tanks it's best to build them whenever you get the chance except when they can only go in the flanking lanes.
Finally if a level is without tanks just bum rush with rilfemen and assault squads through the center lane and you can win two or three levels easily that way.
I found that the 20% reduction in unit cost and the air strike upgrade were the best ones.
I finally beat the 101, but I didn't get a badge!
Useful tip : Use swings or trees instead of crates for cheap blockers (covers 2 vertical and 2 horizontal rather than just one square. For the same price!)