Zoop - America's Largest Killer of Time!

Zoop is a frantic action puzzle game in which you control a small triangle trapped inside a shrinking play field. Coloured shapes creep in from all four sides, and your only defence is to fire your own colour at them: matching pieces vanish, while a different colour swaps places with you. The tension comes from how little time you get to think. Rows advance relentlessly, and if any shape reaches the inner square the round is over. It became a cult favourite precisely because its simple rule set turns brutally demanding within a few levels.