Up
In Combinatorial Game Theory UP is the name of an infinitesimal, also written ^. UP is defined as
^ = { 0 | * }
Left (Black) can play to 0, while Right (White) can play to * (STAR). UP is positive, favoring Left, who gets the last play, no matter who goes first. The opposite of UP is DOWN, also written v.
Some plays with a miai value of 1 chill to UP. (See Chilled Go). Here is an example.
This position chills to 2^ (2 plus ^). Black can get the last play locally no matter who plays first.
For "Up" as a direction on the board see UpAndDown.