The game is set up as eight worlds divided into four levels each. In each level, Mario or Luigi must run or swim through the level, dodging enemies and obstacles while grabbing power-ups and coins. The game can be played by either one or two players. In two-player mode the players alternate, with player 1 controlling Mario, and player 2 taking control of Luigi. To begin the complete walkthrough, start with World 1.
The standard time limit sequence for levels is as follows:
- World X-1 Time: 400
- World X-2 Time: 400
- World X-3 Time: 300
- World X-4 Time: 300
However, there are six exceptions:
- Worlds 3-2, 5-1 and 8-1 all have clear times of 300. World 8-1 is also notable because it is the longest level in the surface world!
- Castles 4-4, 7-4 and 8-4 are all mazes, and they have clear times of 400. World 8-4 is also the only world where you can be sent backwards!
Because of the programming of the Nintendo system, seconds go at 2.5 times the speed of literal ones. This means that in both Super Mario Bros. 1 and 2:
- All worlds with a time of 400 give you a total of 2 minutes and 40 seconds to complete them.
- All worlds with a time of 300 give you a total of 2 minutes to complete them.
Completing the game in under 10 minutes
It is possible to beat the game in very little time. Official records have been held at 5 minutes. In order to achieve this phenomenal time, you must run as quickly as you can at all times, and avoid anything that might slow you down, such as collecting power-ups or dropping down pipes (unless those pipes lead to quicker times).
World 1-1 - Run from the start of the stage, and take the fourth green pipe from the start, and run quickly through the coin room, and complete the stage.
World 1-2 - At the final part of the level with the orange platforms moving up and down, anticipate their presence and jump to the first set of platforms that are droping, to the top of the blue platform in the middle, to the next set of platforms that are rising, and make it to the top of the screen in one fluid motion.
World 4-1 - Beat as normal. To save time, it is possible to jump over the piranha plants. Your jumps have to be timed perfectly though otherwise Mario will be killed by the plants.
World 4-2 - Towards the beginning of the level, there are a number of "?" blocks with an orange platform to the right of them. Go over this platform and you'll see three brick blocks above you. The left-most block has a beanstalk which will take you to the warp zone for world 8-1. Stand directly underneath the right-most block and jump. An invisible coin block will appear. Go underneath the middle block and a higher up coin block will appear. Now use these blocks that have appeared as stairs. Move Mario so he is standing on the highest "?" block and is underneath the far left brick. Jump to make the beanstalk appear. Destroy the center brick and climb up the beanstalk. Go to the very right hand side of the level and again go down the very left pipe. You will now be in World 8-1.