Very fun game! I loved the main movement mechanic, and I think that the game was very challenging. I liked the upgrade system, it really added to the game. If there were anything I'd change, it's the font used for the letters. Sometimes I'd get confused with an i being an L or V being a U, simply because of the font used. But it wasn't too much of an issue, after a couple minutes of playing I got used to it, so it's not an issue whatsoever really. The music and sound effects fitted the game very well, they felt right at home in this game. I found that killing some of the enemies was very difficult, shooting out so many bullets, with barely any chance to attack. But thats why I love this game, it's a huge challenge, and you really need to react fast and know where the keys are on the keyboard.
Well done, this is an awesome submission to the jam!