In 2010, a little card game caught my eye. Onirim was a small, pocket-sized box that held one of the most addictive and engaging single-player card games I’ve ever played. I gave away the game to a friend shortly thereafter, encouraging her to play it, and thinking that it would be easy to re-acquire. Well, it wasn’t. It took four years for the game to go back into print, but it was well worth the wait.

Now in a significantly larger box, Onirim’s 2014 rerelease includes the same core set as well as its full slate of seven expansions, making it the definitive edition of the game. Players are tasked with finding and opening the eight Oneiric Doors, gates within the land of dreams. Unlocking a door is as easy as creating a set of three cards of the same color, without having consecutive cards bearing matching symbols. You can also open a door if you draw its card and have a corresponding key in your hand. Beware, though: Nightmare cards also lurk in the deck, threatening to undo your progress. If you open all eight doors before the deck runs out, you win. But if even one remains locked when you must draw a card, you remain trapped forever.

Onirim is relatively unique in that it is designed explicitly as a solitaire challenge. The core game is challenging but still winnable with a little experience and skill. Where the game becomes interesting is in the addition of the expansions, which introduce additional effects and twists. For example, one expansion requires you to open the doors in a specific order. Seems like a pretty simple change, right? Well try saying that when you need to open a green door next and you have a hand full of blue cards. The expansions can be added in any combination, making the game as easy or as difficult as you choose.

The game is not without its drawbacks, of course. First, there is a lot of shuffling involved; it rivals most deck-building games for number of shuffles per minute of gameplay. This makes it slightly prone to damage to the edges of the cards early on; worse, the deck size is not conducive to the use of card sleeves, meaning the only solution is caution. The game also has an annoying tendency to either be too easy or completely unforgiving. While it is a game predominantly based on strategy, player choices can become frustratingly obviated when streaks of Nightmare cards show up. Fortunately, the game’s lightning-fast pace smooths over most of these concerns; if you had a bad deal, you’re only stuck with it for about ten or fifteen minutes.

It might seem a little odd for a solitaire game to be considered a must-own for board game enthusiasts, but Onirim is one of those rare titles that combines challenging gameplay with simple mechanics and fast play. Unfortunately, the game’s popularity in the United States has made it scarce yet again, but with a bit of patience you should be able to track down a copy. I can’t recommend enough that you do so. Onirim is a solid fifth-gear choice.