Skip to content

Game Preservation

Jump to bottom
Daniel Nylander edited this page Aug 13, 2026 · 9 revisions

Game Preservation

Documentation baseline: v1.1.126. OpenCaptive uses player-supplied original media and content hashes rather than bundling game data.

This page documents the original Captive and Liberation releases, their platform variants, and preservation considerations.

Captive (1990)

Release history

Year Platform Publisher Notes
1990 Amiga Mindscape Original release by Tony Crowther
1990 Atari ST Mindscape Simultaneous with Amiga
1992 DOS Mindscape v1.06 (Oct 7 1992), LZEXE compressed

Platform differences

Feature DOS Amiga Atari ST
Resolution 320x200 320x200 (256 overscan) 320x200
Colours 32 (VGA) 32 (OCS/ECS) 16 (ST low)
Graphics format PL5 (5bpp packed) IFF ILBM / custom Degas Elite / custom
Animation ANM (XOR delta) IFF ANIM ANM variant
Compression LZEXE (executable) RNC Method 1 RNC Method 1
Sound AdLib/Roland/SB/Speaker Paula 4-channel YM2149
Music format MIDI Amiga module Amiga module variant
Disk format DOS files ADF (880K OFS) FAT12 disk image
Map generation Identical PRNG Identical PRNG Identical PRNG

The map generation algorithm and PRNG are identical across all platforms — the same mission seed produces the same dungeon layout. Visual assets differ in format but represent the same content.

Cross-platform verification: Amiga ADF panel sheet and DOS PL5 panel sheet produce identical 64,000-pixel output (verified by OpenCaptive's captive_panel_match tool).

DOS executable details

Original (packed):    73,056 bytes, LZEXE v0.91
Unpacked:            144,556 bytes
Packed SHA-256:      71bcf404103f1ac2920800a8bc166939bb49a1204cf51bebce8aca7dd5faafde
Unpacked SHA-256:    fa7d5ca76d26f614476ed41f27cf737084942e9216b20b4605734df9ede9aee4

Amiga media

Standard 3.5" DD floppy disk (880 KiB), OFS filesystem. The amiga_ofs_inventory tool inventories content by SHA-256 without using filenames.

Media formats

  • ADF disk images: 880 KB (DD) standard Amiga floppy format, 80 tracks x 2 sides x 11 sectors x 512 bytes
  • LZEXE compression: CAPPO.EXE uses LZEXE v0.91; unpacked SHA-256: fa7d5ca76d26f614476ed41f27cf737084942e9216b20b4605734df9ede9aee4
  • ZIP archive support: OpenCaptive scans ZIP archives with nested file discovery, identifying game resources by SHA-256 regardless of archive structure or filenames
  • Atari ST: FAT12 disk images with BIOS parameter block at offset 11

Preservation status

  • DOS version: widely preserved, LZEXE decompression well understood
  • Amiga version: ADF images commonly available in preservation archives
  • Atari ST version: disk images available, FAT12 format straightforward
  • All versions: map generation verified to produce identical output from same seed

Liberation: Captive 2 (1993)

Release history

Year Platform Publisher Notes
1993 Amiga Mindscape Original release, 5 floppy disks
1994 Amiga CD32 Mindscape CD version with Red Book audio, CityGen 1.12

No DOS or Atari ST version was released.

Platform differences

Feature Amiga floppy Amiga CD32
Media 5x ADF (880K each) 1x CD-ROM (ISO9660 + audio)
Animation IFF ANIM opt5 IFF ANIM (PACK/PALL/SCPT)
Compression RNC Method 1 RNC Method 2
Music Amiga module 10 Red Book CD audio tracks
CityGen Built-in External executable (v1.12, 1994-01-03)
Sprites AMOS sprite bank AMOS sprite bank (AmSp)

CD32 disc structure

Track 01:  Data (ISO9660, MODE1/2352, CDTV extensions)
Track 02:  Audio — Mark Knight
Track 03:  Audio — Mark Knight
...
Track 11:  Audio — Mark Knight

Data track SHA-256: f807b1385c0996d54ed10afab271a7dd31d2c6dc6a18f13196ad2a79a0af8a80

CD32 filesystem contents

The ISO9660 filesystem contains:

Category Files Description
Executable captiveII Main game binary (245,628 bytes, 68000)
City generators CityGen, BuildingGen AmigaOS relocatable executables
3D vectors *.x3g City, room, monster, NPC, object geometry
Wall textures WALL*.VGM VGM format wall textures
Sprites MainSP.Img, MainSP16.Img Sprite sheets
UI graphics 3dView.Img, backpack.img, Taxi.Img Pre-rendered UI elements
Menu GameMenu.spr Menu sprites
Fonts {0-3}Liberation.FNT 4 font variants
Data CityGen, BuildingGen, Wall.Log Generation data and mappings
Saves Lib-Saves/ Save game directory

Amiga floppy media

5 standard 3.5" DD floppy disks (4.4 MiB total):

  • CaptiveII_Disk1 through CaptiveII_Disk4
  • Boot disk
  • OFS filesystem

Media formats

  • ADF disk images: 880 KB (DD) for floppy release, 1760 KB (HD) not used
  • ISO 9660: CD32 data track in MODE1/2352 raw sectors with CDTV extensions
  • Red Book audio: 10 CD audio tracks (Track 02-11) by Mark Knight

Preservation status

  • CD32 version: raw BIN/CUE images preserved; ISO9660 is standard and readable
  • Amiga floppy version: ADF images available; 5-disk set is complete
  • Audio tracks: Red Book CD audio, preserved as part of BIN/CUE image
  • CityGen/PlotGen: relocatable AmigaOS executables requiring 68000 analysis

OpenCaptive's approach to preservation

No original data distributed

Original game data is never committed to the repository, bundled in releases, or emitted by tools. All content is addressed by SHA-256 — the engine locates and verifies resources by their cryptographic hash, never by filename or path.

Content identity

OpenCaptive uses SHA-256 content hashes as the sole identity for game resources. This means:

  • Renamed files are still recognized
  • Repacked archives work transparently
  • Different release dumps of the same content match
  • Corrupted or modified files are rejected

No redistribution

Original game data is never committed to the repository, bundled in releases, or emitted by tools. Discovery tools (amiga_ofs_inventory, liberation_inventory) output only digests and byte counts.

Verification tools

# Verify all known resources
opencaptive --data /path/to/media --verify-data all

# Inventory Amiga media
./build/amiga_ofs_inventory /path/to/media <adf-sha256>

# Inventory Liberation CD32
./build/liberation_inventory /path/to/media

# Extract resource for offline analysis (output stays outside repo)
./build/liberation_extract /path/to/media <resource-sha256> /tmp/output.bin

Visual parity verification

OpenCaptive includes frame-comparison tools for pixel-exact verification:

  • --capture-frame — capture a rendered frame
  • --compare-frames — compare two frames
  • --compare-frames-rect — compare a specific region
  • --extract-dos-vga — extract VGA state from a DOS memory dump

Current verification status:

  • Liberation intro: 320x162 region — 0 deviating pixels (pixel-perfect)
  • Liberation city: 320x167 region — 0 deviating pixels (pixel-perfect)
  • Captive DOS startup and Mission 0001 holomap route-selection boundary: verified against the original DOSBox-X runtime
  • Captive arrival, orbit, landing and first-person dungeon transition: not yet verified end-to-end

The Captive DOSBox-X diagnostic can currently authenticate the original startup through the real Mission 0001 FLIGHT PATH SET state. It does not authenticate arrival, orbit, landing or dungeon entry. Static frames, guessed coordinates, procedural routes and generated status text are not accepted as evidence.

The Captive verification boundary is deliberately conservative. FLIGHT PATH SET, a static orbit reference or an unchanged memory dump does not prove that the ship arrived. Original runtime state and original VGA output must both change before a later phase is accepted.

The same rule applies to landing and dungeon entry: a water-only landing, hard-coded coordinate, generated map, replacement marker, or synthetic status message is not valid evidence. Tests stop at the last state that the original DOSBox-X runtime actually produced.

External references

Clone this wiki locally