coefficient of friction seems inconsistent between levels. L pieces stay on circles at sharp angles but two circles keep rolling off an almost perfectly flat surface even when they're weighted down.
17 is harder than 18. Boss on 18 has 3.2 million health, but he doesn't move and he doesn't attack very often. I accidentally used a bunch of dryads though and magic gives him extra health...oops
Speed run with flamethrower is so much fun. Beat 17 waves with gold suit. Would have gone farther but I was stuck with the gatling gun for the first 10 waves. The homing missiles are underpowered, but they are nice because they let you focus on dodging shots instead of aiming.