This is a very enjoyable and fun little game and I like it a lot! The game do starts a bit slowly but it started to get better and better once you goes on a few tries and started to grasp what the game is about. I eventually got score of 2550 which I guess is not too good. The visuals in the game although simple somehow looks very pleasant, especially the special effects which I think contributes the most to the nice feel of the game.
For some feedback, I think the game do feels a bit slow concerning the difficult increase. Dragging on more than 10 mins I think do not benefit the game at all, and I rather prefer that fast to lose and start again mentality. I would also say that the game would benefit with more enemy types, and I would also suggest adding rare enemies that seldom appears, but would be much harder to deal with.
Anyway, I think you did a good job polishing the game and really make something very good in that short 14 days time limit. Well done!