your game is working well, here is my feedback...

• good music and sound effects
  
• cool art style, it is distinctive and has a cool vibe
• i like the little story in the start of the level, just enough to get players interested
• you could add color to some things like the player and enemy bullets, explosions, powerups, etc
• i think the color pops could add a lot visually while also helping with gameplay, like i had trouble seeing bullets
• you should make the mouse also work to control, this could even work on touch devices, wasd would be good too
• there is no reason to not shoot all the time, maybe a charge shot or bullet economy would help with strategy

Your game is like mine, I loved everything!