isle/docs

LEGO Island File Format Documentation

This folder contains documentation for LEGO Island's custom binary file formats using Kaitai Struct, a declarative language for describing binary data structures.

What is Kaitai Struct?

Kaitai Struct allows you to define binary formats in a YAML-based .ksy file, which can then be:

• Compiled into parser libraries for many programming languages (C++, Python, JavaScript, etc.)
• Visualized interactively using the Kaitai Struct Visualizer
• Dumped to human-readable formats using ksdump

Documented Formats

File	Extension	Description
savegame.ksy	.GS	Main game save data (game state, progress, customizations)
players.ksy	.gsi	Player profile save data (usernames)
history.ksy	.gsi	Score history and high scores

Using the Tools

Installation

See the Kaitai Struct Visualizer installation instructions for setup details.

Kaitai Struct Visualizer (ksv)

The Kaitai Struct Visualizer (ksv) provides an interactive terminal UI for exploring binary files.

# View a save game file
ksv samples/G0.GS savegame.ksy

# View a Players.gsi file
ksv samples/Players.gsi players.ksy

# View a History.gsi file
ksv samples/History.gsi history.ksy

Kaitai Struct Dump (ksdump)

ksdump outputs the parsed structure as JSON or YAML for scripting and inspection.

# Dump a save game to JSON
ksdump --format json samples/G0.GS savegame.ksy

# Dump Players.gsi to JSON
ksdump --format json samples/Players.gsi players.ksy

# Dump History.gsi to YAML
ksdump --format yaml samples/History.gsi history.ksy

Sample Files

The samples/ directory contains example save files for testing:

• G0.GS, G1.GS, G2.GS - Sample main game save files (slots 0, 1, 2)
• Players.gsi - Sample player profile data
• History.gsi - Sample score history data