Per request, the rules for Power UNO: You play like reguluar UNO, execpt there are extra rules. There are only three, but they make the game so much more complicated, so I'll try and cover all the problem scenarios, too. Sometimes, you just have to play it to get the hang of it.
1) If someone plays a card and you have the exact same card in your hand, you can play it, even if it is not your turn. Play then continues as if it had been your turn. This means that you have to play quickly, because you might get skipped otherwise. Say someone plays a Red 7, and you have a Red 7 in your hand, but it's not your turn. (I need illustrations!) You can play it, but only if you get it onto the pile before the person whose turn it really is. If it's your turn, you need to get your card onto the pile as soon as possible, because someone else might be able to jump in and play a double card, and you would, in effect, lose a turn. If you have two of the same card in your hand, you can play them in the same turn, but you have to lay them down one at a time. No laying down two cards at once.
2) If a Draw Two card is played, and you have a Draw Two of any color in your hand, you can play the Draw Two and play passes on until a player does not have a Draw Two to play, and they must draw the sum of the cards that have been played. So if three people in a row lay down Draw Twos, and the fourth person does not have a Draw Two, he/she must draw six cards. I think we've had people have to draw up to fourteen cards before. The only way to get out of a Draw Two pile is lay down a Reverse of the color that was just played, to reverse it back onto the last person who played. So if that third person layed down a Yellow Draw Two, and the fourth person had a Yellow Reverse, he/she could play it and the third person would have had to draw.
Things get complicated when you combine those first two rules, because you can always play a "double" card. If there is a Draw Two pile going on, anyone can jump in with the same card. So if play is going to the right and you lay down a Blue Draw Two, and the person to your left has a Blue Draw Two, he/she can lay it down and play continues to you. If you don't have another Draw Two, you will have to draw four cards. Same goes for the Reverse. In that Yellow scenario above, if anyone in the game had the other Yellow Reverse, he/she can lay it down, and one of the players beside them (depending on which way the play is flowing) would have to draw.
This rule also applies to Draw Fours. If someone lays down a Draw Four, you can pass it on if you have a Draw Four. You can also reverse the draw. If you have a Reverse card in your hand of the color the person calls, you can reverse that Draw Four right back onto the person who played it.
3) The last rule is a little easier. If you play a Zero card of any color, you can call time-out and exchange hands with any player at the table. So if you have twenty cards in your hand, and the player across from you has only three, play that Zero and switch. It doesn't work so well if you have two zeros in your hand, because that player might be able to play the Zero you gave them and switch right back.
There is another thing, because I'm not sure what the official rules say: we play that if you don't have a card in your hand that you can play when it's your turn, you draw until you can play. There's some strategy involved, since you don't have to comply with all the rules. You don't have to lay down a double if you don't want to. Say if you have a double card in your hand and the person whose turn it is has to draw, you can hold that card while they draw cards, and you can decide whether or not to play it until another card is played. You can let them draw seven cards and then play the card. It will make you an enemy, but you can do it. You don't have to switch hands when you play a zero, even if someone has less cards than you.
We also call time-out when someone has to draw a bunch of cards, to let them organize them. Since you have to be aware of what is in your hand at all times, it's a good idea to at least organize by color, preferably also by number, so you know if you have doubles in your hand. You're at a disadvantage if you have a drink or food at the table, because if your empty hand is occupied with holding a glass, you might miss out on an opportunity to play. Especially if you're playing with experienced players. And I have to warn you, this game can get violent. I think my sister still has a scar from when Mom drew blood trying to play a card.
Thanksgiving, we were playing with so many people, we had to get out a second deck. That was crazy, because then there are FOUR of the same card. Ever see four people trying to play the same card at once? Then we had to figure out who played the last card to figure out how play resumed. I got a few 'oohs' and 'ahs' when I speedily played the four Yellow Five cards in my hand in about three seconds.
Good game.