A game of Pegs.
The idea is to jump over pegs until there is only one left. The green dots are pegs. The yellow hole in the middle is the only free space to jump into at the start. You can only jump over a peg if the pegs are next to eachother. The peg that is jumped over is removed. Diagonal jumps are not allowed. To jump over a peg, click on the square containing the peg that will do the jumping - in the direction which you would like it to jump.