It was quite an ambitious thing for a first finished game, so you aimed high! It seems to work mechanically as well, once you've figured out the camera pans.
There were choice to make, in terms of the units to spawn, but I couldn't see much difference between the different types - they all just seemed to explode when hitting an enemy, perhaps if the more expensive ones could take 2 or 3 hits that would have helped. It was tough to win, once the red guys got to the centre and started shooting then you could never catch up as your blue guys just died and there was no tactic to get out of that. Well done for finishing though and keep working on it if you want to make improvements