But the video of [Tiburcio de la Carcova] building up a mini-Galaga cabinet (complete with actual tiny CRT screen from an old ... of Raspberry-Pi-powered video game emulators on Hackaday, so ...

During the Galaga demonstration, wait until the Galaga Commander uses the tractor beam. Before it sucks up the ship, press fire and kill it. You now have total control and can play the sample level.