Maybe ~25%? I made a very simple editor to make the graphics (Every individual graphic of the game will be made with only one polygon, so I made a polygon editor). That is finished.
I think the most important part of the code is already implemented, but really its impossible to tell if my estimations are right. One never knows when something that you didn't expect will come up.
Maybe, one advise to everyone: Don't think too much about percentages and design documents. Start working on the game now, we only have less than a moth left. JUST DO IT.