Game materials
Two standard Poker decks with different back (say, red and blue), without J’s, Q’s, K’s and Jokers, for a total of 80 cards.

Card features
The card in play will be distinguished by three important features:
· the value, from zero to the value of the card (10’s are considered as 0’s, as we are about to see);
· the nature, which can be of red matter (if the card is of Heart or Diamond suit) or black antimatter (if it is of Spade or Club suit);
· the colour of the back, important for the final scoring.

Game preparation
Choose randomly the first player to start. This player will shuffle the deck and deal five cards to himself and to the other player, putting the rest of the deck at the centre of the table, face down.

Card auction
At the beginning of each turn, the current player reveals some cards from the face down deck and puts them at the centre of the play area, clearly visible to both players.
He will keep revealing cards until there are three cards with the same colour of the back. So, in each turn three to five cards will go to the auction.
Then, players take turns in offering for getting (or avoiding) the cards at the auction.

Step 1: Offerings
The first offering is up to the current player. He may put down a number of cards (from no cards at all to ten cards) to declare his offering.
The offering value is given by the last digit of the sum of the offered cards. For example, if the offer is made up by the cards 1, 3 and 8, the sum is 1+3+8=12 and the last digit is 2, so this offering has a value of 2. The value of an offering with a sum of 10 is zero (e.g. 7 and 3), and so on.
The opponent can answer by playing a higher number of cards, regardless of the value, or by passing. Each auction bid, however, can be done only by adding cards to the cards already played (if any): you cannot change the cards already played to form your new offer.
The auction keeps going until both players pass. At the end of the auction, one of the following situations occurs:
1) both players offered a number of cards different from zero: the auction is won by the player with the highest offering value. In case of a tie with values different from zero, the auction goes to the player offering more cards. If the offering value is zero for both players, the auction goes to the player offering less cards.
In any case, the auction winner gives the cards he offered to his opponent and collects the auctioned cards in his hand. The player who lost the auction gets back the cards he offered.
2) a player offered at least one card, while the other player offered no cards: the first player collects the auctioned cards in his hand, and puts the offered cards in a pile near the deck (this pile will be called the deposit).
3) no player offered cards: the auctioned cards are added to the deposit (the pile of cards near the deck).

Step 2: Matter and antimatter
Now, look at cards in players’ hands.
Each pair of cards with the same value and of same nature (for example, a 2 of Spades and a 2 of Clubs, or two 9’s of Spades) is put apart, face up, and will be worth positive points.
Immediately after, each pair of cards with the same value but of different nature (for example, an 8 of Hearts and an 8 of Clubs) is put apart, face down, and could be worth negative points. When this happens, we say that those two cards exploded, due to the contact between matter and anti-matter. Not very scientific, but very functional...
At this point, even cards in the deposit can explode, if they form pairs of cards with the same value but of different nature. The cards exploded in the deposit will be out of play for the rest of the game.

Step 3: Inspection
Now both players (starting from the who lost the last auction) have the opportunity to “call for an inspection”. Who calls for an inspection forces his opponent to show all of his cards.
If among these cards there are cards with the same value and the player holding them forgot to score points for them (for example, he has a 6 of Spades and a 6 of Hearts still unexploded in his hand), then the “absent minded” player loses all of his cards worth positive points he collected so far. If the inspection does not reveal anything suspicious, on the other hand, who called the inspection loses one of his cards worth positive points (if any).
Thus, it is possible to “cheat” in this game, although it is very dangerous! Remember that you can use the inspection just to get an idea of the other player’s resources.

New turn
When all the inspections have ended, if a player has less than three cards in hand, he draws from the face down deck as many cards as needed to reach three cards in his hand.
The player who lost the last auction becomes the first player of the following round and draws the new cards for the auction.

End of the game
If the deck runs out of cards, reshuffle the cards in the deposit and use it at the face down deck. As soon as these cards are not enough to refill players’ hands, the game ends immediately. However, if the deck of deposit cards runs out of cards during an auction, the game continues even with an auction of one or two cards.

Final scoring
After the Step 3 of the last auction, players discard all cards in their hands, and points are tallied: each player gains one point for each positive (face up) card he has collected. Then, look at the back of your negative (face down) cards collected so far and choose one colour to discard: each card of the other card will be worth a negative point. The winner is the player with the highest score. In case of a tie, player who suffered less explosions (that is, the player with less face-down cards) wins.
Example: Leo has collected 26 face up cards and 16 face down cards (9 with blue back and 7 with red back). He chooses to discard the blue back cards, obtaining a final score of 26-7=19.

An example of a game
First round of play: Leo and Ada chooses randomly who is the first to play, and Leo wins.
He shuffles the deck, deals Ada 5 cards and deals himself 5 cards. Then, he reveals some cards to be auctioned, checking the colour of the cards’ back: red, blue, red, red... since now there are three cards with the same back, he stops and the auction begins.

The starting situation is as follows (remember, 10’s are called “0”):
LEO: 2, 4, 5, 8, 0
AUCTION: 2, 3, 5, 7
ADA: 4, 3, A, 4, 3

Leo would like to grab the 5, which will give him points coupled with his 5, but he wants to avoid the 2 which would explode in contact with his 2. So, he offers 2 (he better doesn’t take risks) and 4. The value of his offering is 4+2=6.
Ada holds in her hand two dangerous cards: the 3 and the 3 which would explode at the end of her turn. But she has also the 4 and the 4 which would give her points instead. To get into the auction she needs at least three cards (since Leo offered two cards). She plays then 3, 3 and A. Her offering value is 7.

Leo realizes that Ada is winning the auction and, moreover, she is giving him the exploding 3 and 3. He then tries to increase his offer, adding the 5 and the 8. His offering value is now 9, the last digit of 2+4+5+8=19.
In this way, Leo wins the auction, because even if Ada would offer all of her cards, her offering value would be 5, and it would be not enough to beat Leo’s offer. Leo, then, gives the cards he offered to Ada and takes the auctioned cards. The present situation is now:

LEO: 2, 3, 5, 0, 7
AUCTION: -
ADA: 2, 4, 4, 3, 5, A, 8, 3, 4

Leo does not gain nor lose point.
Ada puts apart, face up, the pair of two 4 which are worth 2 positive points, but she sees the 3 and the 3 exploding in her hand, and they could be worth negative points at the end of the game (however, having both the red back, they could be both discarded during the final scoring).
Normally, Ada could have bluffed at this point risking an inspection, but she knows that Leo has just seen the pair of 3’s of different nature.

Having lost the auction, Ada is the new starting player. She reveals three cards with blue back and puts them in the auction. The situation is:

LEO: 2, 3, 5, 0, 7
AUCTION: 2, 9, 3
ADA: 2, 5, A, 8, 4

Ada offers the 5. Leo does not even think of winning the auction, since this will generate two explosive situations (2 with 2 and 3 with 3). However, the 5 offered by Ada is tempting, and to get it he must enter into the auction, otherwise Ada’s offer would go to the deposit. He chooses to play 3 and 7 with a final value of 0.
Ada, anyway, spots Leo’s intents, and adds A and 4 to her offering, thus tying Leo’s offer. Yet, the rules state that “if the offering value is zero for both players, the auction goes to the player offering less cards” – that is, Leo. Naturally, Leo does not want to win the auction, but he had to play four or five cards with a sum of zero and he cannot do this. So Leo wins the auction against his will and pays to Ada the cards he used for the offer.
The situation becomes:

LEO: 2, 2, 5, 9, 0, 3
AUCTION: -
ADA: 2, 5, A, 3, 8, 4, 7

The 2 and the 2 explode in Leo’s hand, and he puts aside both cards face down: they could be worth negative points for him.
The game is still open...