Level 16 is awful. First it forces you to use mostly crypts, then throws barbarians first, then rogues. And it follows it up with amazons. I think it's fairly telling that all the guides I've seen have the player at rank 41.
The keyboard controls are really appreciated when working out the earth levels. One thing about the timer-it would be more speedy if the default behavior was just place bomb with 0 seconds, and have the option to change the timer.
After doing the end levels my own way, I looked at the walkthrough and saw them being done a completely different way. Bravo good sir. Awesome game. The dialogue is hilarious.