skids/assets/README.md

Game assets

Everything the game uses is stored here as editable files. The build embeds this folder into the executable. To pick up changes:

• Rebuild: cargo run --release.
• Or skip the rebuild: run with --data assets. Files given with --data override the built-in copy.

These files were converted from the original Amiga disks with skids extract --data <folder with the ADFs>. That conversion is lossless, and running it again overwrites your edits.

Tracks: tracks/<name>/

track.png

The track picture: 1024 × 512, a 16-colour indexed (palette) image.

• Palette: the PNG's palette is the track's palette. Change a palette entry to recolour every pixel that uses it.
• Road vs scenery: colours 8–15 are road; colours 0–7 are scenery, where cars throw up dust. The picture doesn't affect handling. The walls come from the gates (below).
• Painting a new route: paint it with the upper eight colours and update the gates to match.
• Saving: keep the image indexed if your editor allows it. If it saves as full-colour RGB instead, each pixel is matched to the nearest default colour, which loses your palette.

track.txt

Plain text; lines starting with # are comments.

• gate x1 y1 x2 y2: lap gates in race order.
  • Gate 0 is the start/finish line, and the grid forms up behind it.
  • Cars must cross every gate, in order, to complete a lap.
  • Walls: the gates' ends also shape the road. One edge is a smooth curve through every gate's first end (x1 y1), the other through every second end (x2 y2). Those curves are the walls, and computer drivers follow the road between them. The curves pass halfway between neighbouring gates' ends and round off the corners, as in the original.
  • Coordinates are on the isometric ground plane. To find where a point on the ground sits in the picture, with z its height in pixels (from height): picture x = wx - wy + 512, picture y = (wx + wy) / 2 − 156 − z.
  • skids trace --data assets --track N --out t.png draws the walls (grey), the gates (gate 0 in yellow) and the computer cars' paths over the picture.
• height: 64 rows of 64 numbers giving ground height in pixels × 64.
  • Layout: the rows run along world y and the numbers within a row along world x. Each covers 16 × 16 world units.
  • Effect: climbing slows cars and descending speeds them up. Cars leave the ground over crests that drop away faster than gravity, and the car sprites tilt with the slope.
• set: the name of the set of tracks this one belongs to, shown under the menu thumbnail.
• start, flags: values from the original data that the game doesn't use.

thumb.png (optional)

The track's 123 × 32 thumbnail from the original track-select screen, in the track's palette. It's drawn at double height in the menu, because the original's pixels are half-width. Without one, the menu shows a shrunken track.png.

To add a track, make a new folder with track.png and track.txt. Tracks are listed in name order.

Vehicles: vehicles/<id>.png and <id>.txt

<id>.png

A 2048 × 800 sprite sheet: 32 headings across by 25 tilts down, each cell 64 × 32.

• Colours: use only palette indices 0–3:

  • 0 transparent
  • 1 tyres / shadow
  • 2 trim
  • 3 bodywork

  The colours in the file are only a preview; each player's car is recoloured at run time.

• Headings: column 12 faces right, and columns advance clockwise in 11.25° steps.

• Tilts: row = roll × 5 + pitch (each 0–4), so row 12 is the car on flat ground.

<id>-menu.png (optional)

The car's 64 × 32 picture from the original select screen, in the same four colours as the sprite sheet.

<id>.txt

The display name, driver and handling:

Setting	Meaning
name	name shown in the menu
driver	driver's name, shown next to it
trailer	yes for something towed behind cars (the caravan) rather than driven
handling	the 16 values from the original .set file, used as the original game uses them (below)
mass	weight when cars collide; not from the original data

The handling values, counting from 1:

Value	Meaning
1, 2, 6	computer drivers: drag, grip, power
9, 10, 11	human drivers: drag, grip, power
3	steering: 16 = 1/64 of a turn per frame at full lock
5	gravity: 8 = 1 pixel per frame²
7	tow hitch distance behind the car: 2 = 1 world unit
4, 8, 12–16	unused

What the driving values do:

• Drag (below 64): how much of the engine's speed survives each frame. Low drag gives fast pick-up and fast slowing.
• Power: what the throttle adds.
• Top speed: power × drag / (64 − drag) / 32 world units per frame, at 50 frames a second.
• Grip: how quickly the car's movement turns to follow where it's pointing. Low grip means long slides.

The menu's Handling option can replace every car's values with one of the original's presets.

Older files with original, top, accel, brake, grip, turn and offroad lines still load: original is read as handling, and the others are ignored. To add a car, add a new <id>.png / <id>.txt pair.

Sounds: sounds/*.wav

8-bit mono WAV files at the original Amiga sample rates. A loop point, stored in the WAV's smpl chunk, makes a sound repeat from there; most sample editors keep it. The game uses these names:

Sound	Use
motor3	engine, pitched up and down with revs (falls back to motor, then engine)
screech2	tyres sliding (falls back to screech3, then screech)
crash1, crash2, crash3	collisions, picked at random
backfire	lifting off at high revs
horn	Right Shift (player 1) or Left Shift (player 2)
beep, beep2	countdown, then lights out

Missing sounds fall back to synthesised ones. Any other WAV files are kept but not used.

Music: music/*.med

The tune, an OctaMED module. Edit it in a tracker that reads MED files, such as OpenMPT. The game's player supports plain sample instruments (no synth sounds) and the commands listed in docs/FORMATS.md. Preview it with skids music --data assets --out tune.wav. If there are several files, the first in name order plays.

Pictures: gfx/*.png

Indexed PNGs. skidtoon.png is the title picture at the top of the menu, shown at half size. The others aren't used:

• ball.png: 64 frames of a spinning ball with the Acid logo, 16 frames across, each 32 × 33. Its real colours aren't known, so it has a grey palette.
• chat2.png, mouse.png, sign.png: small odds and ends.

Palettes: palettes/*.pal (optional)

16 lines of RRGGBB. Each file overrides the PNG palettes:

• track1-3.pal: one track
• track1.pal: every TRACK1 track
• default.pal: all tracks