Ever been outsmarted by a shark? This poor diver just got hit with a 90-degree counterclockwise rotation. The matrix (0 -1; 1 0) transforms coordinates by rotating them 90° counterclockwise, turning (x, y) into (-y, x) . The shark clearly majored in linear algebra before deciding to terrorize underwater photographers. Next time you're diving, remember to bring your inverse matrix... or just swim faster than your mathematically challenged friends.