Very cool game for your first game :) Reminded me of binding of isaac :D
I love that you made the art yourself, it gives the game a really unique retro vibe :)
A few things I would recommend:
- The enemies are sometimes spawn inside the player, one solution could be to define multiple spawn areas and only spawn in areas where the player is not.
- The different rooms could have different mechanics, like traps you have to dough
- hold the button to shoot balls
- The end could have a big enemy as a boss, this would round up the experience
Overall great game ! keep up the good work :)