itch.io

I'll give you a hint: After you run out of ammo, try dying. It helps.

If you're still lost, you're supposed to shoot down as many enemies as possible. You'll quickly run out of ammo, and you'll have to die. When you die, a clone of you appears, that will repeat your past actions. You'll have more ammo and will be able to gun down the enemies left with it. When all enemies are dead, the red door opens and you're able to jump up to the exit door.