In the 1820s, Charles Babbage conceived of a computer made entirely of mechanical parts. The eccentric genius never actually built his “difference engine,” but Apple software engineer Andrew Carol has picked up where he left off— with Legos.

Carol’s brick-by-brick homage can evaluate polynomials of the form ax2+bx+c, producing answers for each successive value of x with 20 turns of the crank.

His latest version— his third upgrade in six years— uses about 2,000 Lego parts. Carol acknowledges that his computer isn’t as powerful as Babbage’s would have been. “His would have been made of brass,” he says. “Mine’s made out of a plastic children’s toy.”