I know how everyone is saying the game is hard, but to be honest, I found it easy. I plopped the normal towers on the right and left sides of the map and put the fire towers in the middle. From there it was like the game took care of itself. It was a bit tricky early on, but well-placed bombs meant that enemies were not getting close to the castle. It was easy enough to reach the "You win" screen.
A fine job, overall. You got the mechanics of a tower defense down well. You kept it simple and reasonably effective. The addition of limited bombs helped to cover for early game weaknesses and is a good mechanic to add on.
Notes:
- I found trying to click on a tower to build AND having the airship move towards the bottom-right corner to be annoying at times.
- I had to go to full screen to play the game.