# UP

Difficulty: Intermediate   Keywords: EndGame, Theory
For “Up” as a direction on the board see Up and down.

In Combinatorial Game Theory, UP is the name of an infinitesimal, also written . UP is defined as

uarr = { 0 | ast }

Left (Black) can play to 0, while Right (White) can play to ast (STAR). UP is positive, favoring Left, who gets the last play, no matter who goes first. The opposite of UP is DOWN, also written ↓.

Some plays with a miai value of 1 chill to UP. (See Chilled Go). Here is an example:

2 + UP

This position chills to 2↑ (shorthand for 2 + ↑). Black can get the last play locally no matter who plays first.

### Notes and discussion

Robert Pauli:
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