great game!
you really have to think about what you do. Even using one certain tower and strategy doesn't work. you have to actually place towers after thinking about what would be best for that spot. One complaint I do have is that some combinations work well for all situations, such as giving the beam tower fork and giving the sentry two optimizers and the splash upgrade... Also, why isn't splash compatible with the ping tower? I do have an idea on how it could work (every enemy hit takes has a splash damage shockwave spread out) Either way, great game, and I'm looking forward for a possible sequel! :D