The game challenges you to a musical duel with Sans, the character from Undertale. Choose the game mode you prefer, either story mode or free-play mode. Also, choose a song and begin the battle. Press the arrow buttons in the order shown on the screen. Try not to make many mistakes, otherwise, the game will be canceled and you’ll have to start all over again. The game has a story mode plot as well as a wide range of settings – you can customize it to your liking.