Originally posted by DahrkDaiz

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Here's a little lesson on "adding" things to SMB3...

This is your ROM

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Those are memory "blocks" in the rom. You have a set amount of memory blocks, it cannot increase (well it can but that's far beyond the scope of this lesson). Here is a representation of level data in the SMB3 ROM

[L][e][v][e][l][1][X][L][v][l][2][x][L][e][v][e][l][t][h][r][e][e][x][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ]

As you can see what I've done is shown that each level takes up a set amount of level space. Level 1 takes up more than level 2. Level three takes up more than level 1. The X's represent the "end" of that block of data. It tells the game where to stop reading data and putting it in the current level. Let's say you add two enemies to level one. This is what it will look like when you save your rom.

[L][e][v][e][l][1][e1][e2][X][l][2][x][L][e][v][e][l][t][h][r][e][e][x][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ]

e1 and e2 represent the new enemies you just added. But notice, the X and the L are now gone, they were over written. There's now a new X that's where the old "v" for level 2 was. What does that mean? When the game loads level 2, it'll start where the old "L" was and as we can see, it reads e2 instead and then an X, making the level shorter than it really should be. The game only knows where to load levels that the original programmers set, it cannot magically figure out where the next one is if you increased the size of another. So as you can see, adding enemies or level data is not possible without advance techniques. (keeping track of pointers yourself, moving data around, it can be very messy for a beginner). However, you can delete data still. Lets see what happens when you delete a few objects in level one.

[L][e][v][X][ ][ ][ ][L][v][l][2][x][L][e][v][e][l][t][h][r][e][e][x][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ]

As you can see, the level is smaller and the X is closer to the beginning. What this means that as long as the size of the original level is the same or lower, you can delete objects and then add them somewhere else IN THE SAME LEVEL. I hope all this makes sense.

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