Standard Uno rules, PLUS:

1. Stacking. If you have more than one card of the same number, you can play them all at once.
    1a. An even number of reverses played at once means your turn again.
    1b. This includes 7s and 0s even when the rule modifying those cards are in use. Their effects are multiplied.
    1c. If you stack draw cards, it operates as if you bounced yourself. 
    1d. You can skip yourself with this.

2. Bouncing. If someone plays a draw card on you, you can play another one and make the person after you draw double.
    2a. It must be the same amount. You cannot place a +2 on a +4 or vice versa.
    2b. If the player bounced to has a draw card, they can play it on top of the previous two and the player after them draws triple. If that player has yet another draw card, it becomes quadruple, and so on.
    2c. This can be combined with stacking. You can place down multiple draw cards at once.
    2d. This also applies to skips. Same as draws, each skip played adds another player skipped.
        2d1. You can skip yourself with this too.
    
3. Challenge. If someone plays a +4 and you have reason to believe they could have played another card, you can challenge it. If you're right, they draw 6. If you're wrong, you draw 6.
    3a. Bouncing counts as a valid reason to play a +4.
    3b. This does not apply to +2 or any of the special wild cards that make you draw. +4 only.

4. Guess top. At the beginning of each game, guess the top card before it's turned over. The player who is closest goes first.
    4a. If the card turned over is a draw card, it counts as what it is for guessing purposes, but no one has to draw.
    4b. Skips also have no effect, but reverses do.
    4c. +2 is adjacent to 2, but it is not 2. Same applies to +4 and 4.
    4d. If one of the special cards is turned over, it's inserted back into the deck and another card is turned over.
    4e. "Wild" counts as closest when no other guesses are the correct color AND no other guesses are within 2 numbers of correct.
    4f. If the card is a Wild card, non-numbers are close. Low numbers are next closest. 

5. 7-0 rule. In games with 3 or more players, playing a 7 means you can swap hands with another player, a 0 means all players rotate hands in the direction of play.
    5a. If you play a 7 you can decide not to swap hands, but if you play a 0 it's forced.
    
6. Jump in. In games with 5 or more players, if you have the exact same card (EXACT same- color and number.) as the one last played, you can say 'jump in' and place it down out of turn. 
    6a. Play now continues from where you are.
    6b. This does not end your turn automatically. You can still stack. 
    6c. You can continue a bounce this way. Nothing changes about the bounce, the number of cards drawn is preserved.

7. If you call Uno on someone before they do, they must draw 2 cards.
    7a. If they don't actually have Uno and you call it anyway, you draw 3 cards.
    7b. No hiding your cards to try and make someone call false Uno on you. If you do, you draw the penalty the caller would've gotten.

8. Special cards. Most of these are self-explanatory, here's some interesting ones.
    8a. All of these cards act as wild cards, except in the conditions outlined in rule 8b, subsection 2.
    8b. True Wild. This card can be any card you want. Full stop.
        8b1. This card can bounce any other card.
        8b2. In situations where the True Wild is used as a non-wild card, it does not act as a wild card.
    8c. Swap Hands. This does not operate like the 7 in its modified form as detailed in rule 5a. If you play this, swapping is mandatory.
    8d. Draw 1d20. Roll a d20 and draw that amount. If no method of randomization is available, this defaults to draw 10.

None of these rules apply if it's independence day in your country, it's snowing outside, or you've laid down a royal fizzbin this game. On Leap Day, Pi Day, the Ides of March, Presidents' Day, Leif Erikson Day, and all throughout Secretarial Appreciation Week, only even-numbered rules apply. On the 31st of any month, only odd-numbered rules apply.