GEM 

Copyright (c) 2003 Bill Taylor

Gem is actually two twin games (Gem-Y and Gem-EE) played on the following 5-side board.

 

TURN - On each turn, each player drop one friendly stone in an empty cell. GOAL Gem-Y game: a chain of adjacent stones touching 4 sides, or any side and its opposite 2 sides. Gem-EE game:  a chain of adjacent stones touching 4 sides, or 2 groups touching 3 sides each.

 

An Gem-Y example Black just dropped the marked stone threatening to connect two edges at the corner (thru the green dots). White can try to prevent it by playing at [1]. If Black drops at [2] then [3].