  This paper considers a game version of the general position problem in which
a general position set is built through adversarial play. Two players in a
graph, Builder and Blocker, take it in turns to add a vertex to a set, such
that the vertices of this set are always in general position. The goal of
Builder is to create a large general position set, whilst the aim of Blocker is
to frustrate Builder's plans by making the set as small as possible. The game
finishes when no further vertices can be added without creating three-in-a-line
and the number of vertices in this set is the game general position number. We
determine this number for some common graph classes and provide sharp bounds,
in particular for the case of trees. We also discuss the effect of changing the
order of the players.
