Hide a photo in a field of parallel lines, then squint to see it reappear

Draw Celtic knots freehand: strokes become woven ribbons, and a tap on a crossing flips which strand passes over

Feed in any text and dial up the gibberish index to generate new phrases in the same style

Print and fold lenticular pictures that change as the observer moves

Quantise a photo to black and white and trace it into a vector drawing, downloadable as SVG or PDF