L29 - Hit the first (only exposed pipe). Once the 'wall' has been exposed and you can access the 2nd pipe you must hit the 2nd pipe before all the boxes finishes exploding, this grenade should break the 'door' then the last box will fly sideways killing the top man. Leave your aim at the same spot and fire the next grenade which should fall to the bottom and kill the last guy!
29 is by far the hardest level in the game!
Very easy to get the badge, just purchase the 'Pancor Jackhammer' plus either an 'Extended Magazine' powerup or 'Speed Loader'. Spin around and kill everyone in sight!
I agree with the comment about how BTD3 is way easier than this version. Hard on that game was easy, Hard here might as well be impossible!
Fun game though :)
Super easy, all I did was get a bucket load of helicopters and a lighting thing near the end. Once you've got the choppers in place all you do is wait until the end. Very boring, most of the time the action was off the bottom of the screen anyway.