Great game! Looks really good too. One thing I can say is to make it more responsive - clicking on ammo/etc should have some kind of feedback (a sound, particle, light, etc) rather than waiting 5-6 seconds until getting any response.
Yeah. It feels awkward that the game makes it seem like it's click to get ammo, but it's click to move until your player touches it. It'd be cool if you could give the player the option to choose the ammo then choose the tower, then the player would run over and do it, or at least if it popped up with some kind of response (particles, sounds) where you clicked either way.