Tweens is a solitaire game I invented over the last couple of days. Any resemblance to similar games is purely coincidental.

Tweens uses a regular deck of 52 cards. To set up, shuffle the deck thoroughly. Place seven cards face-up in a column, each on top of the last, so that every rank is visible. Repeat until you have six columns of seven cards each, all face up. Also, place two cards face up in front of you, beginning two discard piles. There should be eight cards left in the deck.

The object of the game is to clear all six columns by discarding all of the cards in those columns. You do this by taking pairs off of the columns and placing them in the discard piles, one on each pile. You are allowed to take a pair of cards if the difference in their ranks is the same as the rank of one of the cards on top of the discard piles. (For this purpose, Kings count as 13, Queens as 12, Jacks as 11, and Aces as 1.) This rule has one exception: if a King is visible on the discard pile, you may discard any two cards whose ranks match.

If you're stuck, or you don't want to remove a pair from the columns, you may take the top pair from the deck and put one card on each of the discard piles. If you're stuck and have exhausted the deck, you've lost. If, however, you clear all six columns, you win.

I've found this game very satisfying; each position is amenable to deep analysis, as most of the game's information can be seen at any time. You have to think ahead to play successfully. It seems that most games can be won - but not easily.