Use W,A,S,D, to navigate. Press the space bar to activate the pen. Press the F key to deactivate the pen. Use the number keys 1,2,3,4,5,6,7,8,9,0 to activate different colors. Have fun and make some art! To reset the drawing, press the green flag again. It sort of works like etch a sketch.
Let us know if you want any changes made like controls, bug fixes, more colors, etc. Try a similar game my friend @ZimmermanTKA made here. http://scratch.mit.edu/projects/12912517/