Mario Bros./Walkthrough

The Sewers
Throughout the game, Mario and Luigi's scenery stays constant. Early in the game, the pattern on the pipes changes every few rounds, but the layout never changes. At the top of the screen are two S shaped pipes from which the pests pour out. At the bottom are two pipes which the pests use to exit out of the screen before pouring out of the same side pipe at the top and continuing on. Pests walk in one direction, and drop down to the next level when they reach the end of the pipe they are crawling on. The pests will continue in their direction unless they hit another pest or coin, at which point they will about face and head off in the other direction. In order for Mario and Luigi to clear each round, they must eliminate every pest that the round contains. To do so, they must jump up and punch the pipe directly underneath the pest until they flip over on their head, and then jump up and kick the pests off the screen by running in to them. If Mario kicks off multiple pests consecutively within a second or two, he scores bonus points in multiples of 800 (800, 1600, 2400, up to 3200.) Every time the brother remove a pest, a coin enters the level from one of the top pipes and moves in the same fashion as the pests. However, once they reach the bottom pipe, they exit the screen and disappear for good, so collect them if it is safe to do so for 800 points.

After Mario and Luigi have occupied a round for a long period of time, fireballs begin to appear. Red fireballs continue to ricochet around sewer while green fireballs bounce from one side of the screen to the other. After the second Bonus stage, Slipice begins to appear in search of a location to plant himself and freeze a pipe. Until he manages to completely freeze the pipe, the brothers may interrupt him and punch him from underneath. The pipe will only remain frozen if Slipice has been given enough time to do his work. At higher levels multiple fireballs begin to appear making it more urgent for the brothers to complete their work quickly. The POW block in the center should only be used in the case of emergencies since it's presence creates a relatively safe island for Mario to stand on and punch pests from underneath. It can be hit three times before it disappears. It is occasionally replenished after a Bonus stage. Another semi safe place for the brothers to rest is the middle ledge that occupies the sides of the screen. Other than fireballs, only flies will infrequently make it to this ledge on their own accord.

Bonus Stage
In round 3, 8 and every few rounds thereafter, the brothers are presented with a bonus stage. In here, they will have 20 or 15 seconds to collect 10 coins that are placed throughout the stage. They will always be in the same place every time. A bonus of 800 points is provided for every coin captured, while an additional bonus is awarded if all ten coins are obtained. The first bonus stage gives 3000 points for a perfect run, and every bonus stage after that gives 5000 points. However, after the first bonus stage, every subsequent bonus stage is frozen, so you must plan carefully because it will be much harder to stop and turn around if you've made a mistake. Often it is better to continue going in the direction you are and loop back around to pick up a missed coin than to try and reverse your direction.