MRGN

The locations. A StarCraft 1.00 map has 64 slots and a Brood War map 255. Slot 64 is Anywhere, the whole map. An unused slot has no name and no size.

The elevation word works the other way round from how StarEdit shows it: a set bit leaves out that elevation, so 0 means the location covers every elevation. Conditions such as Bring only count units on the elevations the location covers.

Name	`MRGN` (4D 52 47 4E)
Size	20 bytes per location.
Read by	The game.
Required	Yes. The game does not load a map without it.
More than one copy	Every copy is written over the start of the same fixed-size space, in file order, so a later copy replaces only as many bytes as it carries.
In scmJS	Read, and written again when you change what it holds.

Each location:

Offset	Type	Holds
0	i32	Left edge, in pixels
4	i32	Top edge
8	i32	Right edge
12	i32	Bottom edge
16	u16	Name, a string number
18	u16	Elevations the location leaves out (below)

Elevations:

Bit	Meaning
0x01	Low ground
0x02	Medium ground
0x04	High ground
0x08	Low air
0x10	Medium air
0x20	High air

Example#

A location covering five tiles across and four down, for ground units only. The right and bottom edges are the pixel just past the last tile, and the elevation word lists what the location leaves out:

   0  40 01 00 00  left 320 px (tile 10)
   4  80 01 00 00  top 384 px (tile 12)
   8  E0 01 00 00  right 480 px: tiles up to 14
  12  00 02 00 00  bottom 512 px: tiles up to 15
  16  05 00        name: string 5
  18  38 00        leaves out low air, medium air, high air