In game theory, a game tree is a directed graph whose nodes are positions in a game and whose edges are moves.
The number of leaf nodes in the completegame tree is called the game tree complexity.
Game trees are important in artificial intelligence because one way to pick the best move in a game is to search the game tree using the minimax algorithm or its variants.
In baseball, a completegame (denoted by CG) is the act of a pitcher pitching an entire game himself, without the benefit of a relief pitcher.
As the 20th century went on, completegames became less and less common, to the point where a good pitcher typically achieves only 1 or 2 completegames a season today.
To put in perspective, as recently as 15-20 years ago, 10-15 completegames a year by a star pitcher was not unheard of.