Lust Planet

Besides the in-game instructions, the main objective of the game is collect "eromones" to repair your ship. You can find them laying around, by killing enemies, or fucking Sexliens, the inhabitants of Lust Planet. You can also befriend Sexliens and build a harem in your spaceship, just need to fuck them with the correct rhythm and they'll become your crew.
There's no ending or progress besides 3 easy collectibles, but you can still have fun creating your randomized harem of sexy aliens.