kyoumachi / felinesystem2

An open source remake of the CatSystem2 visual novel engine.

FelineSystem2

An open source remake of the CatSystem2 visual novel engine.

Demo

A makeshift demo of the current version can be found here.

Controls

Click/Scroll - Advance text

Ctrl/Enter - Advance text, hold to skip

SPACE - Hide message window

f - Toggle fullscreen

1-9 - Select choice

Shift + Alt + 1-9 - Quick save to slot 1-9

Shift + 1-9 - Quick load from slot 1-9

Features

• Multi-platform (WASM, Windows SDL2)
• Raw KIF archive decryption
• HG-3 image decoding and caching
• Custom-built CatScene recursive-descent parser

KIF Database Structure

FelineSystem2 implements a custom database of the game's KIF archives and assets, stored as a binary file.

Archive Table

Data Type	Value	Description
char[len]	ArchiveName	NULL-terminated filename of the KIF archive
uint32	EntryCount	Number of entries in archive
unsigned char	IsEncrypted	0x01 if archive is encrypted, 0x00 otherwise
byte[4]	FileKey	Blowfish key for decrypting entries (Only exists if IsEncrypted is 0x01)
0x00	TableEnd	Signifies end of table

Archive Item Entry

Data Type	Value	Description
char[len]	FileName	NULL-terminated deobfuscated filename
uint32	Offset	The offset to the entry's data
uint32	Length	The length of the entry's data

Notes

Parser

• If statements must contain a whitespace after the closing parenthesis of the condition
• Operators follow C-Style left-to-right precedence and associativity
• Integers are the only data type that exist
• Variable names can only be integers
• Variable names can be dynamically evaluated

Special Thanks

• Trigger for creating such an amazingly comprehensive knowledgebase of the CS2 engine
• asmodean for being a pioneer in reversing the CS2 engine
• Dodder for Hacking the Grisaia for localization
• koestl for his impeccable translations and contributions to localization