A friend and I discovered a fun game: coming up with new rock-scissors-paper style triplets. I'd already heard of microwave-cat-tinfoil (which even uses the same hand signifiers as the old standard), but it turns out it's not hard to think of more. When confronted by an eroding cliff, we got water-rock-glass. Seeing a shrub forcibly growing through a hole in a fence, we got plant-fence-rabbit. I explained this to Robert, and he said "Let's play arbitrage!".