Use arrow keys to move around. Press and hold space to shoot. Press E to reload. Don't touch projectiles/enemies. NOTE: If you die on stage (phase) 3, press the flag twice. I cannot fix the issue in which the additional enemies stay after restarting.
I "reused" some aspects from @DudeGuyPersonMan, check his stuff out. This game is what I stole from: https://scratch.mit.edu/projects/752269294/editor/