Could this be the shortest demo ever? Yes, this is on the “high-speed” version of the game (“throttle monkey”), and I did kill the tanks as fast as possible, but my very first try at the demo on normal wasn’t much longer (30 secs?). The demo ends after you kill four tanks, so it’s possible to play longer, but only if you suck.
It was pretty fun, but maybe at the 40 second mark you realize there’s nothing else to do. The game got pretty mixed reviews, although it’s only $5. Eh.