This is not the game, it's a guide of how you can add yourself in the game. You can find the game here: http://scratch.mit.edu/projects/16092110/ I have left inside only the things that you must change, with help for each one. It's not very difficult to do it. The difficult part is to find the sprites you want. Using e.g. Window's Paint, you can put the characters into the karts. Read the instructions carefully, and then apply the changes to the game you have remixed. As you can see inside, every character has its number, so it's very important NOT to change their order. You will need: 6 character sprites (up, upleft, upright, left, down, right), a sound file ( in .wav), a minimap icon and a position portrait.
Add yourself (or your friends or whoever or whatever you want) in 3d Mario Kart!!!!!! Look inside for details... If you have any problem, feel free to ask. Add a link in the comments with your remixed version
