The pump spinning top that hummed on floors on both sides of the Iron Curtain in the 80s - the юла, in Russian. There are two here, rebuilt from photos of real ones: the Soviet top in striped anodised aluminium, and a West German one by LBZ in printed tin (turn your sound on). Pump the knob: drag it up, then push it down fast - or tap it, a stroke for each tap. It takes a few: each quick push spins the top faster, and a slow one adds nothing. Let go and the Soviet top spins on its point, humming, and slowly stands itself up straight - then it wobbles wider and wider, falls, and rolls round on its rim. It stays up only while it spins fast enough: below eight or nine turns a second its lean wins, and over it goes. The West German one spins in the red stand it came with until it runs down, its reeds sounding a chord that thins as it slows. Tap a spinning top to catch it, and tap one at rest to swap it for the other. On a computer, Space or Enter pumps, Escape catches and C swaps. The sound is the air the spinning top throws out of its slots: through the Soviet top's three it sounds the hollow body, as blowing across a bottle does; in the West German one it passes little metal tongues, like a harmonica's.