Each round everybody sees the same question and its unit, for example «How many keys does a standard modern piano have?».
Type your guess and change it as often as you like until you lock it. The round ends when everybody locked or when the time is up; a guess that is not locked still counts.
The closest guess scores 3, the second 2, the third 1. Equally close guesses share the place and its points. An exact guess scores 2 more. No guess, no points.