WOW, good job!
This game is enjoying! Simple mechanics yet effective Gives nostalgia! Good game-loop and it fits the theme somewhat by scaling units.
Here's some critique:
The shooting mechanic is unsatisfying, it scales based on how fast you can click your mouse (which I realize while writig fits the theme perfectly lol). BUT to me it's a very annoying mechanic and also unfair to players.
I think the controls would be better if you faced the same direction as where your mouse is, instead of facing either of the 4 sides.
Besides that a well made game!