There is one thing that is inevitable in the world of computer gaming: if a piece of hardware exists, someone will attempt to run Doom on it. It is such a constant that there is an entire Tumblr blog dedicated to documenting every single platform that has had a version of Doom on it, and even some things that can't run Doom but at least tried. This inevitability goes the other way, too: if it exists, someone will try to port it to Doom. Even back in the earliest days of Doom, people were recreating Wolfenstein 3D levels, then Duke Nukem 3D, then Quake, then Quake 2, then Half-Life, and the list just goes on and on and on. There are Doom-engine implementations of Pac-Man, Tetris, Sonic the Hedgehog, even a handful of aborted attempts at Super Mario Kart. And, yes, the game of Solitaire...but not as you've seen it before. (Presumably. Maybe you have. I'm not psychic.)
I may have lost this game, but man, look at that stack. That's a nice stack.
Rats Solitaire, by the author known only as Isle, brings the classic game of Klondike into a whole different perspective, in the most literal sense of the phrase. When the game starts, you spawn on top of a kitchen counter, next to a hot stove (where it's entirely possible to die if you stand on it for too long), where a green felt tableau and an undealt deck of cards await you. Pressing the "use" key on the deck automatically deals out a round of Klondike, permanently stuck to Deal 3. From there, your goal is the same as any other game of solitaire, except for the fact that you are barely 4 inches tall and carrying cards so large that they almost fill the screen when they're in hand.
Filling an empty tableau pile.
Because this is a Doom level, you might expect there to be monsters to fight off, but no such thing happens in Rats Solitaire. No, the most dangerous thing in the oversized kitchen is the risk of slipping off the counter and falling to your death, or hopping into the kitchen sink and going down the garbage disposal. It could be surmised that these are just fun substitutes for the "New Game" button, since there's not much reason to venture away from the tableau otherwise, unless you need a different view of the cards (which, outside of the Ace of Spades bearing the familiar Doom logo, are very much patterned after Susan Kare's CARDS.DLL graphics).
The fact that you are so small, and the cards are so huge, means that seeing the whole play field is quite the challenge. Isle does appear to have thought ahead in this respect, as there are a handful of vantage points to which you can jump. There is a conveniently placed stack of Doom crates for a quick peek, or for more intrepid kitchen explorers, the top of the fridge offers a birds-eye view of the situation (from which you might need to use ZDoom's console to zoom in, unless you've got a very high-resolution monitor).
The garbage disposal is one of a handful of ways to, um, restart the level, if you should need to. What a way to go.
As crazy as the actual proceedings of solitaire are in Doom, the real crazy part is just how much work went into this thing. It must be said that Isle is something of a script-editing prodigy; the Doom engine was never, ever meant to do something like this, even with the enhancements afforded by the updated ZDoom engine. It's far from trivial to just place a card in the world, let alone one that can be picked up and moved. Isle even recreated the famous win animation, with the added ability to fling cards around yourself in any direction you like. The game even has options for it to keep score and a running timer, which helpfully add a handwritten index card and a digital clock next to the stove...appropriately sized, of course.
The view from the fridge makes you feel larger than you really are. Just be careful not to fall off.
The moral of the story, then, is that one should never believe it when someone says that something is impossible. Someone will find a way. It just takes finding someone crazy enough to try it.
Want to play this one for yourself? Get it from the /idgames Archive, and make sure you've got a copy of Doom 2 and a ZDoom-based Doom port.