Basic tower defense game, but maybe I'm just a sucker for the genre because I played through all five levels and enjoyed it quite a bit! I wish there had been a little more strategic variation -- the weapons just seem to differ in terms of range, fire rate, and (maybe) damage; it would be cool to have weapons that allow for synergies, like one that slows down enemies, and maybe an area of effect weapon.
Also, it appears to be 3D but we're locked into a top-down pseudo 2D view. It would be cool to be able to move the camera and get a better view of those penguins and bears! (It's hard to tell what they are from the bird's eye view.)
Also *please* add a little 5 second or so period at the start of the level before enemies come so the player can get a couple of turrets down! That was always the hardest part of each level, having to rush to stop the immediate flow.
All in all, fun! Congrats on your creation :)