Thomas's girlfriend Sylvia has been kidnapped by the mysterious Mr. X and is being held at the top of his dojo. Thomas must journey from right to left (and from left to right on the even-numbered floors), defeat the Kung Fu Masters at the end of each floor, and save Sylvia at the top of the dojo.
One interesting aspect to the gameplay of Kung Fu involves the different point totals you receive for defeating enemies with different moves. Thomas can punch or kick, crouch to do a leg sweep, or do a jump kick. Punches are worth more points than kicks because the enemy needs to get closer for you to perform the move. There are some particularly high-scoring maneuvers: on the second floor, balls fall from the ceiling and erupt into Dragons when they hit the ground. Kicking the Dragons before they disappear results in 2000 points, while kicking normal thugs gives you only 200. There's also a time bonus for quickly making it through a floor, and a health bonus for the health Thomas has remaining. It seemed to me that it was more profitable from a score perspective to hurry through the floors as quickly as possible, rather than "farming" the endless enemies with crouching punches.
After a few attempts, I managed to get to the fourth floor pretty consistently. The poisonous moths that emerge on that floor were no real problem, but the boss was a different story: the Dark Magician. If you kick him in the head, his head falls off and he reveals himself as an illusion, appearing once more, with head intact, a few feet away. The only move that truly damages him is a crouching punch, and in order to safely pull that off you need to do some bobbing and weaving in order to avoid his fireballs, which he throws at a couple different angles.
Mr. X on the fifth floor is a very defensive fighter... but he seems to be weak to sweep kicks, because spamming that move allowed me to defeat him pretty handily. My daughter Naomi was over that morning, and if anything she was even more excited about my victory over Mr. X than I was. Another thing that she was really amazed at: after you win, Sylvia gets kidnapped again and you have to play through the game again! This is pretty standard stuff for games from the early to mid Eighties (and especially for arcade ports), but for a six-year-old today that's apparently a big Plot Twist.
The internet tells me that if you play through the game fifty times, then Mr. X is replaced by Sylvia at the end! I don't know if that's true or not; I might do some research after this to see, but even with a game length of about ten minutes, I don't think I have the patience (or the skill!) to try that feat for myself.
Here's the score for my winning run, which came to an end halfway through the second loop:
10/15/15 LYS (2-4) 225,420
I'm pretty happy with Kung Fu. It is a pretty simple and fast game, but that makes it snappy, and I could see trying for score on multiple loops being a fun enough diversion.
