-Visuals are very appealing. Animations are simple, yet effective.
-Music is catchy.
-Gameplay is repetitive, but not in a bad way. The quick mini-tutorial goes nicely and the random spawn enemies makes it to where you can't just muscle-memory things (obstacles seem to be the same, though).
-Upgrades: You used a simple upgrade system, which is fine. Also, unlike other games, the upgrades have an actual effect.
-The only real 'upgrade' that I can think of for this game would be just a status bar with your current run meter, but that's nit-picking.
Bottom line: Awesome game that's quick to pick up and easy to lose yourself in. It's fun to play and makes you WANT to keep playing to try and win. Great submission!