Many adult engineers used to be child engineers, working in Lego and other building toys. Many adult engineers have not abandoned their love of those toys. A few of those engineers combine their childhood and adult passions to build computing devices out of toys:

• Martin Howard built Lego logic gates (and a Lego Rubik’s cube!).
• Andrew Carol built a Lego difference engine.
• Tim Robinson built a Meccano difference engine.
• William Hilton built a K’nex adding machine.