Click the green flag. (You will start out in editing mode.) Click the green flag 3 times and go fullscreen, this will help with lag To switch between the pen color use the number keys. 1 for Platform 2 for Water 3 for Obstacles 4 for Finish 5 for Eraser (To erase all press... up,up,down,down,left,right,left,right.) R will restart the level. H will hide the editing menu. Press the space bar in play mode to switch to editing mode.
