I just finished the game for the second time. Here are my thoughts:
A fun shoot em up! You shoot little creatures and a huge boss to get to the next wave. The gameplay is simple and fun. It would be more fun if the map was a bit more advanced. Maybe an arena?
The movement was kind of stiff, like there was a delay between me pressing the button and the character moving. The character moved left 2 seconds after I pressed the button. That did not feel good.
The art is simple, bright and cute. It gets the job done. But the fact that there was no music or sound effects was really disappointing. Shooting the enemies and the boss in total silence felt very awkward. You could have easily obtained those from a website like freesound.org, opengameart.org, or FreeMusicArchive.org . The game would be 10x more fun if there was a catchy music and some sound effects like shooting, boss getting killed etc. Maybe you were running out of time, or maybe you didn't know about these websites?
Overall, I think what you did was decent. Your gameplay is pretty good, every single wave was fun. But the movement, audio and level design could use a little more work I feel. However, you put this game in such short time, which is a huge accomplishment. You should be proud of your work and use this as a learning experience. I hope you get to work on a lot of other fun projects in the future!