Tien Len can be considered the national card game of Vietnam; the name of the game, means Go Forward. Probably as a result of the Vietnam war, Tien Len has spread to some parts of the USA, and sometimes it is also called Thirteen.
Tien Len is a climbing game (like Zheng Shangou, Big Two, Tichu, Gang of Four, or President) in which the aim is to get rid of your cards as soon as possible by beating combinations of cards played by the other players. Its distinctive feature among those games is the use of various pair-runs like 2-2-3-3-4-4 to trump single and pairs of 2s.
The game is for four players. A standard 52 card deck is used. There are no Jokers and no wild cards.
The ranking of the cards is: Two (highest), Ace, King, Queen, Jack, Ten, Nine, Eight, Seven, Six, Five, Four, Three (lowest).
Within each rank there is also an order of suits: Hearts (highest), Diamonds, Clubs, Spades (lowest).
Among climbing games, Tien Len's most distinctive feature is its unique mechanic for "bombing" the high deuces: a 3-finger run (e.g. 445566) trumps a single 2; a 4-finger run (e.g. 44556677) trumps a pair of 2's; a 5-finger run trumps a trio of 2's; and a 6-finger run beats a quad of 2s.