For every level except the final one, I'd recommend taking it slow and capturing catapults one at a time, and you will eventually get to the end. Personally, I think it took me longer to complete the last level than it did all of the previous ones put together (at the hardest difficulty).

When it comes to the final level, I spent so long trying to capture the catapults one at a time, and found that even on my good runs, it was still taking far too long and that I'd run out of time before beating the level. Instead, the strategy I recommend for it would be to capture every power-up you can and hope to get either a shield or a time freeze. Once you do, quickly run up the map, making sure you capture the side with the boss on it. Then it's a simple matter of cleaning up shop.


Good luck!