If you use WASD F-attack Space-Jump and Arrow keys R shift-jump R enter-attack you can play against yourself. I figured this out because no one would play with me anymore after I beat them too much. Tip:Don't beat your one friend too often at a game. he'll stop playing with you.
I just downloaded and quickly figured out I could play by myself but I'd love for their to be a bot or maybe online capabilities. This game is so fun so far and any one of those two additional features would make this game even better!