- Joysticks: The left joystick controls Mario's movement while the right joystick controls Luigi. Push left or right to make the brothers run in either direction. If you run off one side of the screen, you will reappear on the other side. There is no up or down in this game.
- Jump: Pushing this button makes Mario or Luigi jump. If the button is pushed alone, the brothers will jump straight up, but if the joystick is pressed right or left, they will perform a running jump in either direction.
- 1 or 2 Players: Push these buttons to begin a one player game or a two player simultaneous game.
Mario and Luigi
You take control of Mario as player 1, or Luigi as player 2, as they attempt to rid the sewers of the pipe pests. Controlling the brothers is simply a matter of pushing left and right to make them run, or pressing the A button to make them jump. Momentum is a factor in Mario Bros. and the brothers don't exactly stop on a dime, especially if there is ice beneath their feet so plan accordingly. Jumping allows the brothers to reach higher pipes, but if a pipe is overhead, they punch a bump in to the pipe that can knock a pest back, or even on it's head. The only thing that the brothers can safely touch are coins. Mario and Luigi, like everything else in the game (except fireballs,) can wrap around from one side of the screen to the other.
These are the first pests that the brothers will encounter. They are simple enough to defeat. One punch from underneath flips them on to their shells, and one kick after that sends them flying. If they manage to get back on their feet, they go from green to purple and speed up a bit. If flipped and righted once more, they turn red and become exceptionally fast.
These crabby pests begin to show up after the first bonus stage. They are similar to Shellcreepers except they take an extra punch to knock them on their head. They start out calm, but after being punch once, they become angry and speed up. They will only flip over after being punched a second time. If they flip back to their feet, they turn blue and speed up again. If it happens yet again, they turn pink and are at their fastest.
The final pest form arrives in the third stage after the first bonus stage and adds a new wrinkle to Mario and Luigi's job. Like the Shellcreepers, they only require one punch from below to flip them on to their head. But unlike the other pests, they keep bouncing off of the ground, so they are only vulnerable to the brother's attacks when their feet are firmly planted on the ground. Punching them while they're in the air is ineffective. Therefore, time you attacks carefully in order to rid the sewers of this overgrown menace.
If Mario or Luigi sticks around in one stage for too long, things start to heat up, literally. Two forms of fireballs appear, each with a distinct color and behavior. The red fireballs are slow and bounce around diagonally all around the board. If they hit one side of the screen, they ricochet off the side and keep going. On the other hand green fireballs appear on one level and quickly bounce all the way from one side of the screen to the other and disappear. Both pose a threat to the help of the brothers, but both can be eliminated with a well timed punch from below. However, in order for the punch to be effective, either fireball must be touching the pipe when the brothers jump, or the attack is ineffective. After a fireball is destroyed, it stays out of play for a few moments, only to return much faster the next time it appears.
Slipice begins to show up after the second bonus stage. Like fireballs, it only takes one hit from below to get rid of him and unlike fireballs, he sticks to the ground, so it's pretty easy to hit him. However, if he is left alone for too long, he will eventually find a pipe that isn't yet frozen and freeze it solid, covering the pipe with a film of ice. This makes the pipe very slippery and gives the brothers a much harder time coming to a stop when they are running. They are a minimal threat, so don't go out of your way to get rid of them, but any chance to do away with one is worth taking.
After the third bonus stage, the top of the sewers become very cold, and icicles begin to form on the top pipes and highest platform. A drip of water begins to accumulate before it freezes in to a point. After hanging on for a few moments, it drops to the floor, causing harm to Mario or Luigi if they are hit by the falling spike. If the brothers jump up and punch the water before it freezes, they can cancel the formation of the ice. Once the icicle has formed, be sure not to stand underneath its path to the ground. The icicles glitter in the light, so get to know their tell-tale sparkle so that you can avoid them without actively watching them.
In case of emergency the brothers have one extra weapon at their disposal, the POW block. It is always located in the lower center of the screen when it is available, and it can be used three times before being used up. It is refreshed after the second and subsequent bonus stages. Jumping up and punching POW will create an earthquake effect on the entire screen. Any enemy on the ground at that time will behave as if they had received a punch from below. This means that pests knocked on their back or head will be put back on their feet. This is best saved for emergencies or when a high scoring potential becomes available.