Use arrow keys to move and space to shoot. I recreated most of it from memory (in one day for a school project) and it's my favourite arcade game.
*Obviously I don't own the assets to Galaga, credit to Bandai Namco.* Looking back on this project I am realising a lot of ways I could've made the enemies fly in at the start, and fix some issues and make it look better. If I have the time and the willpower I'll probably do that.