Awesome game. I especially liked that you have to use your overdrive strategically and balance between targeting shield enemies and clearing out large groups, while not letting overdrive charge drop to zero. For early concept, well balanced, but there are a few problems:

1.Early game is too slow. Consider making early upgrades cheaper

2. Second cannon upgrade is extremely op. It should be more expensive

3.Bosses are quite easy, because they don't have that much hp. Also they don't do anything, so you could add them some abilities.

I really enjoyed playing! Thanks!