Tip: A combination of Meteor and Terror on boss is quite effective. If you build up right, you won't use your mana throughout the fight. Terror the boss and then use meteorite. Cuts down on time.
The last level doesn't have any blue cars and like, 20 rival cars. I suggest adding a way to save your times, to increase replay value. Great game, love the graphics, and this one was way easier than the first.
Being able to target first or last enemies would be nice. It's aggravating when at the last of my waves one bubble slips by because every tower is shooting on the bubbles behind it.
As long as the Daimyo is uncovered, you can use up your steps and still go back to him. But if you find him on the last step, you lose. And don't make the quit button so accessible in your next game :(. I loved it!