There is a much older Taco Bell grift: the charity coin drop game. Drop a coin onto the bottom step of an acrylic spiral staircase in a little water tank and you get a free menu item based on the denomination of the coin. It was designed so that if you landed on the last 2-3 steps you had a chance, but any higher and the centrifugal force of walking it down the steps would send the coin off the edge. It was very random with poor odds.<p>But eventually employees got sick of changing nasty change water and left it empty. The physics were a little different, but it seemed to be sufficiently difficult. Rather than wafting around, the further the coin dropped the more likely it was to bounce off a step. The much more deterministic coin movement enabled a new strategy: walk the coin backwards off of the first step and catch the coin directly on the final step. After ~$1 of practice, I had years of 5¢ tacos.