A classic Tower Defense game. Can't say much more than that, although this game can get hardcore at times, even on the "standard" difficulty. The game starts slow and easy, but as the levels and waves go up, so too does the difficulty.
Resource management, path tailoring, turret selection and upgrading all make a difference between getting a "gold" ranked completion and failing entirely.
Still getting stuck on levels, as I'm still trying to figure out the best layout and selection for each area, but that'll come in time.