I like your drawings. Hat characters are really cute!
Here is a list of my concerns:
- Enemies walk through the walls.
- Don't make full screen by default, better add button (you can see it in other games)
- Not enough player feedback: ex, add some blink to the player when you're hit.
- I'm not sure, but at start it feels strange, that you move orthogonally but enemies move freely.
- Also I would suggest to always show controls in the game hud. It is hard to remember them and play the game :)
For the first game it is a really awesome work, congrats!