The Opposites Game

About a week ago I played an opposites game in a mixed group with native speakers. It's a game where participants form a circle and ask their neighbour to name an antonym for a word. Americans go heavy on adjectives at first: takai-yasui, semai-hiroi, and so on. Japanese endeavour to be above it. For example, did you know that the opposite for yama (mountain) is kawa (river)? But either way, in a few revolutions the vocabulary gets drained and players start getting creative. I didn't want to do it, because it ran a risk of revealing the power levels, but eventually I resorted to the question from Danna 02. My relay neighbour was a native speaker, BTW.