Galaga is a retro shooting game, similar to Space Invaders but slightly more advanced. The first time I experienced this game was during the loading screens of Tekken, although this doesn't seem as good as I remember.
The gameplay seems fairly slow, and annoyingly; your attacks often go between the gaps of enemies. The enemies fly in from the lower parts of the screen, and move into a space invader formation. Then they begin to break in waves to attack you. Their flight paths aren't linear; they often spiral around, making them hard to hit. Once they reach the bottom screen, they will re-enter from the top.
Most of the initial levels just seem slight variants of the same pattern of enemies so it all seems too familiar, even over a few plays. When I got a bit better at the game, I found myself frustrated that it feels like a lot of effort to go through the first several levels, then you can find yourself losing a few lives too easily. You only have a few lives, so it quickly becomes "Game Over" and then you are back to replaying the first several levels.