finally, TD troops can move
The ability to move makes this game fun. But controlling it felt much more clunky than necessary, mostly because you need to scroll around by moving the mouse to the little arrows at the edges of the screen. Simply having the WASD or arrow keys scroll would have made it easier to control and a bit more fun; shrinking the sprites so the entire map could fit on one screen would have been even better. (If you still want to be able to show off the nice graphics and were really ambitious, you could have the spacebar switch between a close up view for fine control and nice graphics, and a zoomed out view to more quickly and easily control over the entire map.)
And of course like everyone else will probably ask for, more variety in the types of units and enemies, and different maps.