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rgmechex
@rgmechex

Let's revisit the Super Mario Bros. level format. In my video about it, I was able to list out every object in the game along with its ID number since there are so few different objects and tiles in the game. However, you may have noticed some missing.

In the video, I was assuming that the level these objects were to be inserted into was a standard overworld level. But there are other objects that you can only find in different kinds of levels. How do those work?

2 styles of brick blocks; a dirt, seafloor, and castle masonry block; a square block, coral, and cloud block The blocks that make up objects that can appear in different styles in different contexts.

Super Mario Bros. doesn't have any concept of tilesets, so all tiles are available to all level types. So why don't you see coral blocks outside of water or square blocks in castles?


A handful of objects in the game's code draw themselves to video RAM differently depending on different aspects of the current level. It's sort of like tilesets, but not quite. It is true that all tile graphics are available to all levels, but it's the way these object use these tiles that is different. Also, some tiles like the coral block just weren't ever intended to be drawn in say, a normal level, so they look quite weird. (That didn't stop the developers in world 9 of Super Mario Bros. 2 though!)

World 9 of Super Mario Bros. 2, featuring coral blocks above water These coral blocks look out of place even though this is a water level, since it is missing the water backdrop!

Here I'll list the objects that dynamically choose what blocks to use. First up is the bricks.

The row of bricks can show up as three different blocks. If the current level's special platform is the cloud variant of the green tree, then it will show up as a cloud block. This also prevents it from being broken by big Mario. This only applies to the row of bricks specifically. The column of bricks is unaffected by this. However, they are both affected by the second check: if the level is an underwater level, then these will show up as coral blocks. These are also non-breakable. Otherwise, the object will show up as normal bricks.

Rows and columns of bricks, clouds, and coral There are columns of clouds in some of the bonus rooms, but each cloud is its own object.

Now, this only applies to the row and column objects. Bricks with powerups in them will still show up like bricks no matter what. However, all bricks also have one other check, and its one you may have never noticed. If the level is an overworld level, then all bricks will use a graphic that has a shiny top to them. In all other level types, the bricks are not shiny. This is easily noticeable when you have bricks stacked vertically, since the shine prevents them from repeating nicely in that direction.

Brown, blue, green, and gray bricks; only the brown ones are shiny I only noticed this relatively recently--there aren't very many overworld levels with bricks stacked vertically so you can really notice the shiny part.

The next block to show is the plain square block. Again, these checks only apply to the row and column of blocks objects, and not the staircase object. Staircase objects are always made up of square blocks no matter what. If the square block object is in a castle, it will show up as the castle masonry bricks instead. If its in an underwater level, it too will blend in with the floor and show up as the seafloor blocks. Only in overworld and underground levels will these show up as plain square blocks.

A brown and blue square block, a green seafloor block, and a gray castle masonry brick block Fun fact: the gray castle block uses four colors; the black I've added in this pictures is just the background of the castle levels peeking through. They look quite bad on the standard blue background.

And lastly are the hole (without water) and coin objects. Normally, these objects draw air tiles, and coins surrounded by air. But in underwater levels, these tiles are replaced with versions with a blue background. This is because the normal background of an underwater level doesn't use air tiles, but the solid blue water tiles. These objects had to be modified so that they blend nicely into the background without leaving a rectangular hole.

Some coins and a bottomless pit in overworld and underwater styles Also, when you collect these underwater coins, they leave a blue square of water behind instead of an empty space.

There is one more thing though that changes depending on the level properties, and that is the floor pattern. In the video, I showed these off as being dirt blocks, but in the original game, the only floor pattern used with dirt blocks was the standard 2-block high floor (and the completely empty pattern).

The first check is based off of the level type. Overworld levels will use dirt, underground levels will use (dull) bricks, underwater levels will use the seafloor, and castle levels will use the masonry bricks. However, if the special platform is the cloud variant of the green tree (just like before, used in bonus areas), then this is replaced with the cloud block. Additionally, Y positions 8, 9, 10, and 12 will always be air as well. This always leaves a tunnel at the bottom so it can never be completely solid. It also leaves a block at the bottom of the screen empty (so the floor is only one cloud block thick). And then, if this is an underground level, the bottom two rows are replaced with dirt (even in a cloud bonus room). This is how the underground levels can use mostly bricks, but still have dirt at the bottom, while also still being able to use floor patterns to build large brick structures.

Floor patterns made of dirt, bricks, seafloor, castle masonry, and clouds The six types of floor patterns: overworld, underground, underwater, castle, cloud bonus, and underground cloud bonus. These are all shown in their "full 15 blocks" version.

The weirdness of how these objects changes is what causes certain glitch levels to look weird. For example, the start of a castle level that is treated like an underground level lets you actually see the difference between the rows of blocks used for the initial platform versus the floor pattern. In a castle, these two blocks would be the same, but underground, they are different.

A castle glitch level but underground; the starting staircase down is made of square blocks while the rest is made of normal bricks You can see the dirt at the bottom too--that's just part of the floor pattern!

In fact, this is why the underwater room in 8-1 of Super Mario Bros. 2 looks so weird, since you can pick apart these different objects.

An underwater room in Super Mario Bros. 2 featuring castle masonry bricks underwater World 8 has a special case where all floor patterns are treated like a castle. So the seafloor blocks you see here are all square block objects!

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