Peg Solitaire, or simply Solitaire, is a single player game dating back several centuries. Usually played on a board with holes and pegs, or marbles, it can be easily set up with the Green Box.
At a glance:
32 cubes of any colour
Build a cross shaped board with the tiles. Start with a 3×3 center and extend with four 3×2 arms.
Place a cube on every tile, except the center tile.
You play by taking one cube to jump over another into an empty spot. The cube you jump across is removed from the board. Now select another cube to make another jump.
The goal of the game is to remove all cubes except one from the board.
See Wikipedia for more in-depth rules, strategy, history and variations.