Every shape is the shape below it, dragged. A point dragged is a line; a line dragged sideways is a square; a square dragged up is a cube; keep going and you reach the tesseract.
Five rooms: Draw (draw any of 16 shapes with one finger and Tessa names and scores it — with Build and Slice tools inside: extrude prisms, pyramids, a cylinder and a cone, or cut shapes in two and have both pieces named), Dimensions (the ladder from 0D to 4D, every name's story), Quests (stars for true drawings, and folding six squares into a cube — exactly 11 nets), Explore (a searchable wiki of 44 famous shapes, fun facts, and the questions kids ask), and Settings (English, 日本語, 中文).
Works beautifully with Apple Pencil: pressure-sensitive strokes, palm rejection and hover preview.
Free, installable, works offline. No ads, no accounts, no tracking. Part of Zoey's Lab, with Huely (a colour lab) and Ditty (a Morse code lab).