A) Joystick: This controls Donkey Kong Jr.'s movement. Pushing left or right makes Junior run, while pushing up or down makes Junior climb or descend the vines or chains that he's holding.
B) Jump: Pushing this button makes Junior jump. If the button is pushed alone, Junior will jump straight up, but if the joystick is pressed right or left, Junior will perform a running jump in either direction.
C) 1 or 2 Players: Push these buttons to begin a one or two player game.
Donkey Kong Jr.
You play as Donkey Kong's son, Junior. You control Junior with the direction pad. Pushing left and right will make Junior run left or right, and also allows him to grab on to nearby vines or chains and shimmy over to them. Pushing up or down allows Junior to climb up vines or chains, or drop down from them. Junior climbs up vines faster when he holds a different one in each hand as opposed to same vine, but he drops down faster when he only holds on to one. Pushing the button causes Junior to jump. He can jump straight up, or do a running jump in either direction. If there is a vine above him, he will grab on to it. If Junior ever touches a fruit, either by running, jumping, or climbing, he will cause it to drop straight down, taking out any enemies below him for an increasing number of bonus points.
Here is your humbled father, once the proud pillager of carpenters' beautiful girlfriends, now captive in Mario's cage. Junior must reach the key at the top of the first three stages in an effort to rescue him, but only by pushing all the keys in to their locks in the final stage can Junior ultimately free his father.
In his only recorded appearance as a villain, Mario's second game pits him against the player by spawning enemies that track Junior down, or run interference on Junior's way to rescue his father. Mario has a wide arsenal at his disposal, but other than pushing Donkey Kong out of Junior's reach, he remains fairly passive throughout the game.
These are the first dangers that Junior will encounter. Red Snapjaws are intelligent but slow, patrolling their given area and refusing to fall off of vines to their doom. Blue Snapjaws on the other hand are quick but dumb, following one path until they drop off the bottom of the screen. Touching one is lethal to Junior. His only alternatives are to jump over them, drop a fruit on them, or avoid them entirely.
Like the Snapjaws, Nitpickers come in two flavors. The Small Nitpickers show up in the Springboard Stage and the Large Nitpickers show up in the Chains Stage. Nitpickers fly away from Mario and swoop down one level to attack Junior. Small Nitpickers choose one of three altitudes to fly at and fly off the screen while Large Nitpickers zig zag their way down to the bottom of the screen before disappearing. Small Nitpickers occasionally take the opportunity to drop an egg on the lower level of the stage that must be avoided.
Sparks appear in Mario's Hideout. Red sparks carefully follow the circuits they start on and never venture from their loop. Mario sends Blue Sparks after Junior which follow the alternate electrical paths down to the bottom of the screen. They will randomly choose one of the four pathways from the top of the stage, so beware. Touching a spark results in the loss of Junior's life, so jump over them but pay attention to the sparks flying overhead.