I really like the graphics! But wheres the sound? I like the manual how you can scroll up and down, but...the letters are WAY too big and strainful to look at, I'd make them a lot smaller like normal text reading. The character moves wayyy too slow though, and I feel the enemies could move a bit faster too. I found myself quitting after 30 seconds due to how slow the character is.
Give yourself more time when submitting a game for a holiday, plenty of time, even if you think you don't need it. You should finish this game, I want to see what it looks like when it's done! :) Though, you should replace the text in the score counter and coin counter with a basic pixel font over what you have. This game has potential but I don't know what to expect in the gameplay besides shooting. You say it's tower defense, so I assume there will be upgradable towers?
It just looks like a shooter to me, but it's somewhat fun. If you were to add towers and upgrades, putting places in the field where to place a tower along with the other weapons you get, would make for a fun game. Keep workin on it! :)