Retro Video Gamer

Kung-Fu Master is a side-scrolling beat 'em up game produced by Irem as arcade game in 1984 and distributed by Data East in North America. The game was initially released in Japan under the title of Spartan X[a] as a tie-in based on the Jackie Chan film Wheels on Meals (which was also distributed under the name Spartan X in Japan); however, the game has no bearing on the plot of the film outside the names of the main protagonist and his girlfriend, allowing Irem to export the game without the license by simply changing the title.

The players control Thomas, the titular Kung-Fu Master, as he fights his way through the five levels of the Devil's Temple in order to rescue his girlfriend Sylvia from the mysterious crime boss Mr. X. Kung-Fu Master is regarded as the first beat 'em up video game. It had a NES port titled Kung Fu, which sold 3.5 million cartridges. The arcade game also inspired a 1988 French film of the same name.

Gameplay

The player controls Thomas with a four-way joystick and two attack buttons to punch and kick. Unlike more conventional side-scrolling games, the joystick is used not only to crouch, but also to jump. Punches and kicks can be performed from a standing, crouching or jumping position. Punches award more points than kicks and do more damage, but their range is shorter.

Underlings encountered by the player include Grippers, who can grab Thomas and drain his energy until shaken off; Knife Throwers, who can throw at two different heights and must be hit twice; and Tom Toms, short fighters who can either grab Thomas or somersault to strike his head when he is crouching. On even-numbered floors, the player must also deal with falling balls and pots, snakes, poisonous moths, fire-breathing dragons, and exploding confetti balls.

The Devil's Temple has five floors, each ending with a different boss (described as "sons of the devil" at the start of the game). In order to complete a floor, Thomas must connect with enough strikes to completely drain the boss's energy meter; he can then climb the stairs to the next floor. Thomas has a fixed time limit to complete each floor; if time runs out or his meter is completely drained, the player loses one life and must replay the entire floor. Upon completing a floor, the player receives bonus points for remaining time and energy. The boss of the fifth floor is Mr. X, the leader of the gang that kidnapped Sylvia. Once he is defeated, Thomas rescues Sylvia and the game restarts at a higher difficulty level.

Source:  Wikipedia (https://en.wikipedia.org/wiki/Kung-Fu_Master_(video_game))

I remember that in the C64 version, on the first floor, when you press SHIFT+G you will shoot a gun. I think it only works for the first floor.