Move the sprites around. Press space to copy the image inside the red box to the black box. Space = do copy F = do fast copy up arrow = clear colors list down arrow = clear result box While mousing over a sprite, press and hold any of these while moving your mouse left or right to adjust their look: R = rotation C = color shift S = size X = clear all changes (do not hold down)
It works by testing every pixel for every possible color value. This by itself would take a stupidly long time, so I sped it up by making it keep track of the colors it's seen and testing for them first. The squirrel has a lot of unique colors, so expect it to take a long time to copy.