One Foundation is a solitaire or patience card game. The object is to move all the playing cards from the top area to the "foundation" at the bottom.
You can only move a card that is not covered by another, and only if its face value is one above or one below that of the foundation card. If you cannot move any cards then you can click on the pile to turn over a new foundation card, but you only have 16 to call on.
In the partially complete game shown in the screenshot, the current foundation card is the six of hearts. The player now has a choice of playing either the seven of diamonds or the five of hearts.
If the seven of diamonds is played, the following card could only be the eight of clubs. A better choice would be the five of hearts, as the following cards could then be: six of spades, seven of diamonds, and then eight of clubs.
Once no more cards can be played, click on the face down stock to reveal a new foundation card and try again. Continue doing this until either no more moves are possible and all the stock has been used - you lose, or all the cards have been moved to the foundation - you win.
As with any patience, winning doesn't happen very frequently.
One Foundation is completely free to download and use.
One Foundation is a program for Windows 95, 98, ME, NT4, XP, 2000, 2003, Vista and Windows 7. Sorry, but it won't work on a Mac, Android, or Linux.