It's quite likely that before you harnessed the power of mana in Magic: The Gathering, and before you started bluffing your way through Texas Hold 'Em, you played Uno. The playing card equivalent of checkers, Uno relies on primary colors and a zero-through-nine number system to create a fast-paced and accessible competitive experience that carries just enough depth to keep players casually engaged. This sort of low-impact gaming feels like a perfect fit for Xbox Live Arcade, and though a greater level of rule customization would have been welcome, this is still a fun and faithful rendition of a childhood favorite.
Unfortunately, there's no way to give another player a charley horse for not shouting Uno over Xbox Live...not yet, at least.
If you've never actually played Uno, well, we feel sorry for your misspent childhood, but you're lucky because Uno is still easy to pick up and is still pretty fun. A typical game of Uno sees four players being dealt a hand of numbered, color-coded cards, with a face-up pile of cards in the middle and the remainder of the deck on the side. As the turns rotate around the table, each player must either place a card on the face-up pile that somehow matches the last card placed there--either they're the same number or the same color--or they have to draw a card from the deck. This goes on until one player's hand has been reduced to a single card, at which point they are obligated to bring this to everyone's attention by shouting "Uno!" The first player to get rid of all their cards is the winner.
Anyone that has actually played Uno will be able to fill you in on the nuances of how the game is played, including the diabolical action cards that let you skip players, change the rotation, and force other players to draw cards, but they'd all probably give you slightly different information. Someone might tell you that when you don't have a card that you can put on the face-up pile, you have to continue drawing cards until you draw a playable card. Someone else might say that you can avoid the penalties of a Draw Two or a Draw Four card by playing another Draw Two or Draw Four on top of it, effectively doubling the draw and passing it along to the next player.
The funny thing about Uno is that they would all be right, as playing around with the rule set is one of the minor pleasures of the game. The Xbox Live Arcade version gives you the option of tweaking several different variables, including those mentioned above, as well as a scoring system that lets a game of Uno go on for multiple rounds, with the winner of each round accruing points based on the cards leftover in the other players' hands. Tweaking rules can radically affect the tone and the pace of a game of Uno, and though some of the more extreme Uno-rule modifications we've played with are absent here, it's difficult to fault the game for not including an exhaustive amount of customization.