SkyRoads level format

SkyRoads level format

Format type	Map/level
Map type	3D tile-based
Layer count	1
Tile size (pixels)	N/A
Viewport (pixels)	N/A
Games	SkyRoads

The SkyRoads level format is used to store SkyRoads tracks. Only roads.lzs is in this format.

File format

Header

The file starts with a header as follows:

Data type	Description
UINT16LE offset	Offset of this level (in bytes since start of file)
UINT16LE length	Decompressed size of this level in bytes

This structure is repeated until the offset of the first level is reached. The length field indicates how much space is required to store the level data once it has been decompressed.

The levels are stored in this order:

• Demo level, shown after credits in intro
• Road 1, Red Heat
• Road 2, Red Heat
• Road 3, Red Heat
• Etc.

Data

Each road is in this layout:

Data type	Description
UINT16LE gravity	<4 = invalid, 4 = 100, 5 = 200, 6 = 300, etc.
UINT16LE fuel	Amount of fuel. Equal to number of squares the ship can travel forward before running out.
UINT16LE oxygen	Oxygen amount. Roughly equal to the number of seconds before oxygen will run out.
BYTE palette[72*3]	72-entry VGA Palette to use in this level (note RGB values are 6-bit but stored as 8-bit)
BYTE road[]	Road data compressed with SkyRoads compression

Map format

After decompression, road is an array of UINT16LE values. There are seven values per line, and the lines are repeated until the end of the file.

Each value represents a different part of the road surface at that point, and the value is split as follows:

Bit	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Purpose	Unused					Full-height top block	Half-height top block	Tunnel	Top Block colour				Bottom Block colour

• A bottom block colour of 0 means there is no thin bottom block at that location
• A top block colour of 0 means it will use the default top block color
• Bits for full or half blocks can be set simultaneously with pipe bit to make flat-topped pipes

Palette

The palette entries are assigned as follows:

Top block colors: top = white, front = green, right = red, left = cyan, inside = purple

Pipe colors: front = dark blue, inside = blue, top = cyan, top/side = green, side = yellow, edge = orange

Palette Entry	Description
1	Always black (#000000)
2 - 16	Bottom block top faces (15 colors)
17 - 31	Bottom block front faces (15 colors)
32 - 46	Bottom block right faces (15 colors)
47 - 61	Bottom block left faces (15 colors)
62	Top block top face (when not using manual color control in bits 4-7)
63	Top block front face
64	Top block right face
65	Top block left face
66	Top block inside (when top block also has pipe bit = 1)
67	Round pipe front face
68	Round pipe inside
69	Round pipe top face
70	Round pipe top/side face
71	Round pipe side face
72	Round pipe edge face

Certain colors in the palette correspond to special behavior tiles (e.g. slippery, burning, or boost). The special tile colors are listed in the table below:

Special Tile Name	Palette Entries	Description
Sticky	3, 18, 33, 48	Color of the tiles which cause the ship to slow down (default: dark green)
Slippery	9, 24, 39, 54	Color of the tiles which have no friction (default: dark gray)
Supplies	10, 25, 40, 55	Color of the tiles which refill oxygen and fuel (default: blue)
Boost	11, 26, 41, 56	Color of the tiles which cause the ship to speed up (default: light green)
Burning	13, 28, 43, 58	Color of the tiles which cause the ship to explode (default: light red)

Credits

This level format was reverse engineered by Wolfy, with KeenRush working out the map code bitfields and how the palette is used. If you find this information helpful in a project you're working on, please give credit where credit is due. (A link back to this wiki would be nice too!)