When completing a level in Super Mario Bros, a sequence of events will happen:
- Mario will grab the flag
- Mario and the flag will move down until the flag reaches a specific point
- Mario will get off the flagpole
- Mario will walk to the right until he reaches the castle door
- Mario will enter the castle
This was what the developers intended for people to conclude when trying to figure out how the ending sequence worked. However, people figured out there was a little more to the ending sequence then meets the eye. The ending sequence (in a technical standpoint) really goes like:
- Mario grabs the flag
- Mario and the flag will move down until the flag reaches a specific point, OR until Mario reaches a specific point
- Mario will get off the flagpole
- Mario will walk right until he bumps into a solid block
- Mario will be moved behind the background
How this TAS is possible
There are a few key things to mention with this system. Firstly, the flagpole base actually blocks Mario from moving down far enough to reach his point. However it IS possible to have Mario be grabbing the flagpole, AND have reached this specific point for a single frame. This is a well known glitch called flagpole glitch. The second key quirk with this system, which is what makes this TAS possible to begin with, is that when Mario is walking to the castle (aka walking right until he hits a solid block) The game never checks to see if the "solid block" is actually the intended type of block (a brick block) or if that block is even the intended block at all. All the game cares about is that Mario hits a solid block, no matter what it is, or where it is. This block is usually a block placed 1 tile to the right of the castle door, since it is a brick block, it takes the same texture as the castle, making it impossible to tell that it is solid rather then background by just looking at it. There also happens to be another solid block that spawns in the ending area: The flagpole base itself. If Mario was to bump that block however, he would need to be low enough to not snap up to the top of the flagpole base (at least 4 pixels down into the block). Sadly, this isn't possible by jumping from any intended area... But it IS possible by jumping from unintended areas. Or by not using a jump at all, and instead using the upwards velocity gained by bouncing off an enemy.
In short, when reaching the end of the level. I need 1 of 2 things to be the case:
- Mario needs to be at least one block lower that the flagpole base (in the floor)
- There needs to be an enemy Mario can bounce on in the space between the stairs and flagpole base
This trick is called a Full Flagpole Glitch (FFPG)
In some levels, this trick is pretty well known, and easy to achieve compared to some of the other levels. (8-2 for example)
But in others, it requires inhumanly difficult, precise tricks to pull off (1-1 for example)
Console Verification
I have verified this TAS works on console with the official Super Mario Bros. cartridge loaded, on unmodified hardware. I used the TAStm32 to replay it and cannot guarantee it will work with other replay devices (although it should)