Double click the flag. Use the arrow keys to move your "soul". Touch Sans to deal damage to him. Orange bones will not hurt you if you are moving. The green bone will heal you. Your "soul" will get bigger each time you attack sans, to make it more challenging! The blasters will INSTANTLY kill you. If the orange bones get annoying, you can press space to hide them, but that would be CHEATING...
Glitched the game :P