Jason Tung Cheung Mar (traditional Chinese: 周潤發; simplified Chinese: 周润发; pinyin: Zhōu Rùnfā; Cantonese Yale: Jàu Yeuhn Faat) (born May 18, 1955) is a Chinese actor. He is one of the most famous actors in Asia and a major actor in the Hong Kong film industry. He mainly plays in dramatic movies. He won Hong Kong's "best actor" award three times and Taiwan's twice.

Jason T.C. Mar plays Ko Chun, an extremely talented gambler who can guess how the dice will turn out by listening to them rattle in a cup. On the eve of a big confrontation with a famous Singaporean gambler, Ko walks into a trap set by Knife, an avid but a so-so gambler, (Andy Lau) meant for an Indian servant. Struck on the head, Ko suffers from amnesia and regresses to a child-like state. Knife, not knowing who Ko is, takes him in and gives him a name, Chocolate, since Ko now has an over-obsessive love for chocolate. As soon as he recognizes Ko's talents begins to exploit his abilities. This invites further trouble and trauma for Ko leading up to a big finale. Knife is stabbed in the leg, protecting Ko, and he is rushed to the hospital. When Ko finally regains his memories, he appears to have no memory of Knife and of how Knife had saved him and took him in. Ko Chun's driver helps the Singaporean gambler by giving him glasses that can see dots on cards (which tells him if it's a King, Queen, Jack,or Ace). During the big showdown, Ko Chun loses 2 rounds and during the last round, fools the Singaporean gambler thus winning all of the money. Then, the Singaporean gambler is sent to jail because he misunderstandingly shot Ko Chun's driver. In the end, Ko Chun remembers Knife and takes him to Las Vegas to gamble.