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 a shape, Tessa names and scores it), Shapes (the catalogue from 0D to 4D with every name's story), Build (drag a square up until it becomes a cube), Nets (fold six squares into a cube — exactly 11 ways), and Slice (find the hexagon hiding in every cube).
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).