Cannon and Wall seems to only take my money without letting me place anything? Also the level up button seems to be currently misaligned. The zooming in and out feels pretty great, but I think the scrolling the screen should scale accordingly. It feel off if I scroll the screen from far away and the screen scrolls slower than my mouse, or faster when I'm zoomed in close. That's it for now, hope it helps a bit. :3

I feel it's a little awkward that the placement is different on each square, like sometimes it's over the border and into the next one. I'm not sure of the purpose behind that but it's one of the first things I noticed!