Movement seems fairly smooth. General mechanics are hard to comment on since they seem to be "run, jump, shoot" which is pretty standard. I never quite figured out the pattern to when the enemies on level 2 move or stand still.
But I'm going to make a comment on the control scheme that has become a bit of a pet-peeve of mine, especially on itch.io games for some reason. I couldn't really play too far because I tend to play these games on my laptop. My laptop briefly disables the trackpad after a keypress to prevent accidental moving/clicking of the "mouse" when typing. This makes games that use "mouse click to shoot" difficult to play. I could understand that if the weapon were aimed. There's no reason for it when there's no aiming. A mouse is used for positional interaction. If you just need a button to trigger "fire", there's dozens of "buttons" available on the keyboard. Why does everyone seem to go for the mouse?