Memory game, using solid tiles.

This is a two player game, in which you try and match two tiles of the
same color. Each player takes alternate turns, turning over two tiles,
if they match, you get a point, and the tiles are removed from the board.
If they do not match, they are turned face-down again.

Use Up/Down/Left/Right arrows to move the pointer, SPACE to turn a tile
over. To quit the game, press ESCAPE
