Galaga: Hyperspace is a game based on classic shoot 'em up games like Galaga and Galaxian. The goal of the game is to destroy each wave of aliens while avoiding the bullets they hurl your way. Each wave gets more and more difficult, and you can only get hit once before losing a life.
At the command line, type
sudo apt-get install -y xgalaga.
To run the game, make sure you are on the desktop environment by typing
startxand then pressing Enter.
Once you are on the desktop, click on the menu button at the bottom-left and highlight Games. Under the sub menu, Galaga will be an option. Click on it to start the game.