Very nice twin stick shooter! I like the simplicity of it, which is what you were going for. The graphics are very nice! And the upgrade mechanics is pretty good.
I have only one major gripe - the aiming feels very cumbersome. I keep hitting the terrain or shooting over the enemies, especially the flying ones. And I think it’d be nice if the crosshair wouldn’t be locked at a fixed distance from the character.
I think it would be nice if the game paused at the beginning to let you read the tutorial.
I also think the game could use some music!
Very nice job overall, good luck with this game!