Move the 'player' with the mouse. Try and find the walls by staying with the light. Note: This is meant to be from a bird's eye view.
I wanted to see if my "Fast Ray Distance" project could detect the walls faster than marching a pixel at a time in Scratch 2.0, like it did in Scratch 1.x. http://beta.scratch.mit.edu/projects/1225805/ It finds the walls in fewer steps but so far it's slower. It might go faster using vector shapes instead of bitmaps, or detecting the shape instead of color? ...but it may not ever beat scratch 2.0's atomic blocks going a pixel at a time... (because this has to detect black under various sized shapes several times.) but it was fun to try.