<b_jonas> slashlearn euclid//Euclid is a short geeky game in which the goal is to do Euclidean compass and straightedge constructions in as few steps as possible. It runs in the browser, found at "http://www.euclidthegame.com/". It was popular among #esoteric regulars in 2016-07.

OLD="$HACKENV/wisdom/$1"; [ -z "$1" ] && OLD="$(lastfiles)"; NEW="${OLD}s"; if [ -f "$NEW" ]; then echo "«${NEW}» already exists"; exit 1; fi; mv "$OLD" "$NEW" && echo "«${OLD}» -> «${NEW}»"