The rules of Big Two
Four players, each for themselves, with a full pack of 52: thirteen cards each. The threes are lowest and the twos highest: 3 4 5 6 7 8 9 10 J Q K A 2. Between two cards of one rank the suit decides, diamonds lowest, then clubs, hearts and spades, so the 3♦ is the lowest card in the pack and the 2♠ the highest.
Whoever holds the 3♦ leads the first hand of the game, and the first play has to include it. After that, the winner of the last hand leads.
You may play one card, a pair, three of a kind, or a five-card hand: a straight, a flush, a full house, four of a kind with any fifth card, or a straight flush, in that order from lowest. Each player in turn beats what is on the table with as many cards, higher, or passes. A single, pair or three of a kind is as high as its highest card. A five-card hand beats any of a lower kind; a straight is ranked by its run, from A-2-3-4-5 lowest to 10-J-Q-K-A highest, then by the suit of its top card; a flush by its suit, then its cards; a full house by its three and four of a kind by its four. A run does not go round the corner, so J-Q-K-A-2 is no straight.
When everybody else has passed, the round goes to whoever played last: the table is cleared and they lead again, anything at all. A pass is for that turn only, unless the table plays it as being for the round.
The first player to play their last card ends the hand. Everybody else scores a point against themselves for every card left: twice that with ten or more, and three times with all thirteen. Once anybody's points reach the limit, 50 unless the table chose 30 or 100, the game is over and the lowest total wins.