Thorns is a variant on the game Hex. The gameboard is made up of "Thorns", which are squares with triangles on each side. The squares and triangles are arranged in a grid.
Players alternate turns. Each turn, a player marks one of the squares with their symbol (X or O) and draws a line through the square and into two of the triangles on opposite sides. This creates a "thorn". The players are attempting to create a continuous path of thorns from one side of the board to another. Thorns are considered touching if they touch or if their triangles overlap
The first player to create a continuous path from one side of the board to the other is the winner.
Part of the 3M Paper Games Series.