Super Mario Bros./Notes

Hacking the End-of-Level Castles

1) Get some graphing paper, and start cordoning 2x2 squares. Make a 5x5 block of such squares (10x10 overall).

2) Reading right-to-left, from the top row down, you've got the metatile defined by $17DF, $17E0, $17E1, etc......, $17F7.

3) This linear string of 25 bytes can be represented on your graph paper like this:

5 4 3 2 1
10 9 8 7 6
15 14 13 12 11
20 19 18 17 16
25 24 23 22 21

(In other words, the first byte in this string codes for the upper-rightmost metatile, the second byte codes for the metatile directly to #1's left, etc.)

4) The large castles at the end of every X-3 level (and the beginning of most X-1 levels) are simply the small castle stacked on top of another, slightly taller one. This taller castle is 6 metatiles high and five metatiles wide, and is coded in a similar right-to-left, top-down fashion. Its linear byte sequence begins at $17F8.

5) The little side-sections on the X-3 castle type are actually the same background image that occurs throughout World 8-3. This image is 1 metatile wide and eleven metatiles high (although it only appears to be six metatiles high since the first five bytes are assigned transparent "00" values). Its coding begins at $13CE and ends at $13D8.

Here are some metatile values to keep handy:

00: Nothing/Transparent
45: Castle Top, sky background
46: Castle Window (left)
47: Castle Brickwork (generic filler)
48: Castle Window (right)
49: Castle Top, brick background
4A: Castle Entrance (top)
4B: Castle Entrance (bottom)