I never realized how difficult and confusing the controls were for most people. I can assure you that once you get used to them they are extremely powerful, but that doesn't really help you at all.
I will try to come up with a useful tutorial, one that explains the strategies of details of the controls. I guess the most important thing I can do is make sure the players know what they're supposed to be doing!
About the mouse control, well I know it's really weird, and causes a lot of problems. The ragdoll doesn't follow the mouse - moving the cursor 20 pixels to the right pushes the blue ragdoll's head to the right with a proportional amount of force.
Also, since the mouse button is used for crouching, I can't exactly put a menu button anywhere, or else it would be easy to click it accidentally. Instead the menu comes up when the cursor goes off the screen.
Eventually you learn to follow the ragdoll with the mouse cursor. It's pretty messed up, but once you're used to it, it's really powerful. Which, again, doesn't help you much.
Analog control sticks would be the best control scheme for this game. It would probably be a lot better on a console. But I think I'll experiment with controls where the ragdoll follows the mouse.
And let me clarify some things about the game. There is in fact an AI mode, because both players start out being controlled by the AI until someone drops in. If both red and blue (keyboard and mouse) have dropped in, then it becomes a multiplayer game. I'll probably make the AI start out better so it's easier to tell.
Also, you win by reducing your opponent's health to zero. It keeps track of the number of wins for each side, which you can reset by choosing 'new' from the menu.
And I'm still working on the sound. I'm working on programming some music that changes based on how you play.
So, once I get recorded games working, I'll release a movie of me playing against my brother so you can see what the game is supposed to be like!

I think you will be pleasantly surprised.
After that, it's just a matter of making it easier for new players to get to that level of play.
I have to say that max0rz's comment was very enlightening for me. I realized that the game I was designing was structured differently than most games here on NG. It's designed for casual play, and it doesn't quite feel like a full game. I play it for the joy of feeling the *ahem* expertly designed physics, doing flips and handstands and such, setting up a big combo in slow motion.
Other games, even really bad ones, make you feel like you're accomplishing something. Like you're doing a lot, when you're only clicking as fast as you can, for example. I never bothered to even try to do that with my game. I didn't think of it. I just made a game that people who already understand the game and like playing it just for the fun of it, will like.
It was the first time I felt relieved and hopeful about the future of this game since its release, because it pointed towards a concrete direction for me to go with it. I need to show people how much there is to do in this game, because there is a lot more under the surface. I need to add music, to add recorded games so people can use it as an animation tool, as a social tool to show off and share their moves.
So, basically, I need to greatly improve the tutorial and controls, add the other features, and release gameplay videos and stuff to show what you can do with this game.