Simon Tatham's Portable Puzzle Collection is a set of popular puzzle
games for one player including Black Box, Bridges, Cube, Dominosa,
Fifteen, Filling, Flip, Flood, Galaxies, Guess, Inertia, Keen,
Light Up, Loopy, Magnets, Map, Mines, Net, Netslide, Palisade,
Pattern, Pearl, Pegs, Range, Rectangles, Same Game, Signpost,
Singles, Sixteen, Slant, Solo, Tents, Towers, Tracks, Twiddle,
Undead, Unequal, Unruly and Untangle.