@JustAnotherVoice, it actually makes the game easier, because the creep's HP is determined by how many missions you've completed. The more missions you complete, the more creep's HP goes up. You could do the first mission after completing 8 others and the creep's health would start at 400-ish instead of 20.
Also, another thing, I had 2,600 cash when I stopped playing for a bit, then I came back to the game (after saving and all) and I has 128 cash! >:( That needs a fix.
Needs a more in depth tutorial BEFORE you start playing. I would have never known you can link lasers to each other for more damage (and supposedly more range, but that I have yet to see) had I not gone to the Light Corridor Campaign. This is a very fun game with a lot of different towers and stuff to choose from, and many maps to keep you busy.
This is a very nice game, quite a challance, especially on the harder missions. One thing I'd like to see is more credit rewards for completing missions as well as doing things in missions. 1 or 2 credits for destroying a ship/turret/whatever is crap and worthless. 300 credits for a mission that takes a long time is really frustrating. I'd like to see maybe 10 credits per kill or so and about 5-8x more credit reward for mission victory. Also, a 1.5x increase in value limit for ships would be nice too.