Complex sentence: Crypt of the Necrodancer is a video game that is based upon acting to the beat of the music where the only way to do anything is to hit a key/keys in time with the beat of the song.
Split into simpler sentences: Crypt of the Necrodancer is a video game that is based upon acting to the beat of the music. The only way to do anything is to hit a key/keys in time with the beat of the song.