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An open source remake of the CatSystem2 visual novel engine.

Home Page: https://fruit.toori.tech

C++ 53.75% C 43.43% Makefile 0.08% Python 2.74%

catsystem catsystem2 emscripten reverse-engineering sdl2 visual-novel visual-novel-engine wasm webassembly galgame

felinesystem2's Introduction

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
- if (#300==0) #(950+#300)=512
Operators follow C-Style left-to-right precedence and associativity
Integers and strings are the only data types that exist
- #300=0
- str 50 bg02
Variable names can only be integers
Variable names can be dynamically evaluated
- #(950+#300)=512

Script

blend argument specifies the alpha value that the image will be displayed at
- cg 0 blend 255 will display a completely opaque CG while cg 0 blend 0 will display a completely transparent CG
rdraw command after an image specifies the duration to fade to the target opacity
- rdraw 30 will take 30 frames to fade the image from alpha 0 to the target alpha (e.g. 255 by default)
- Units are likely in frames at 60fps (0.0167s/frame) regardless of the game's refresh rate setting
- An rdraw command will apply to all images within a script block (from a user input to the next wait command)
wait command without arguments will block until any time-based command completes
- wait after a rdraw 30 command will wait for the 30 frames taken to completely fade in the images before proceeding to the next command
wait with arguments behaves differently from standalone wait
- wait 60 will block for 60 frames before proceeding to the next command
- wait 60 will not be aware of any time-based commands like rdraw and will not block until rdraw completes
- wait is sometimes used along with wait 60 consecutively
cg 0 attr 1 (70+0) (80+0)
cg 0 attr 2 (75+0) (85+0)
- Assigns the BaseX, BaseY values of the specified image cg 0 to the variables #(75+0) and #(85+0) respectively

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

felinesystem2's People

Contributors

Stargazers

Watchers

Forkers

kyoumachi meowboy326

felinesystem2's Issues

Not all image types are supported

https://github.com/trigger-segfault/TriggersTools.CatSystem2/wiki/HG%E2%80%903-Image

Fetching audio files might be causing delay

No click/touch controls

Possibly keyboard shortcuts

Implement byte range downloads

https://emscripten.org/docs/api_reference/fetch.html#byte-range-downloads

Inequality is not supported by the parser

if(#710<#50) #710=#50

SE does not stop when advancing quickly

Fetch audio
Stop audio (before fetching)
Audio fetched, still plays when it is not supposed to

Fix: use objects to track state

Support ++ operator

#891++

SDL_Delay freezes program

Need a solution that maintains responsiveness

Support frame index selection for images

Assuming index 0 for all assets will cause wrong images to be displayed

SDL_RWops allocated at around 0xa18ad8 will be unusable when calling SDL_RWclose on other locations

Support keyword arguments

eg 0 mode sepia

SDL_Mixer 1 frees memory less frequently

Boolean operators and != are not supported

if(#849==1 && #540!=200)

Support Japanese text and symbols, handle locale conversion

Implement parser

https://unclechromedome.org/c++-tutorials/expression-parser/index.html

Implement animation system

Integrate into event loop
Need to handle logic/rendering

Implement automatic asset scaling to fit window

Handle @ operator

https://github.com/trigger-segfault/TriggersTools.CatSystem2/wiki/Script-Formats

Intensive functions block browser updates

Recursive command parsing take up too much processing and blocks the browser's responsiveness

Implement transitions and effects

Support wait command

Bounds checking is not performed for argument access

Catch failed byte range requests

Sometimes byte range requests fetch wrong lengths of data

Audio is jerky when performing background operations

Some BG are hidden underneath other images in Japanese script

Images are not cleared properly

Implement sprite effects

e.g. manpu, sweat, animated effects

Check for name clashes when populating KIF database

When forcing lowercase names

Some scripts use lowercase asset filenames

Handle this inconsistency

Use an outlined font

Support appended text

Probably \n is not parsed

Create a proper logger that uses console.log

Support string variables

str 60 Juicy-Yuuji
$str60

Image offsets calculation is wrong

Especially CG (x and y positions)

Animations are not implemented

https://github.com/emscripten-ports/SDL2/blob/master/test/testsprite2.c

Implement choice selection

Skipping quickly causes event queue to be overloaded (WASM)

Negative numbers are not considered in regex matching

Handle SE looping and channels

se 0 loop se152b

fg implementation is wrong

fg uses coordinates from the attr command, but the values from attr 1 is unknown.

cg 4 attr 1 (70+4) (80+4)
cg 4 attr 2 (75+4) (85+4)

When fg is used, text is hidden unintentionally for a short moment due to separate sections. This is a text hiding/showing logic problem.

Cache bgm data

Not all commands are supported

Textures do not remain across renders

Unlike in the local SDL application, the emscripten implementation clears the canvas (to black) after every render.

Implement +=, -=, etc. operators

Some backgrounds are invalid

Tiny ~50 x 50px images that do not fill the screen

Handle looping animations

	wait
	bgm 0 bgm03
	se 0 loop se152b
	se 0 fade 0 50 50
	pl 1 blend 0
	pl 2 blend 0
	eg 1 parts_gaitou 512 288 0 1
	eg 2 parts_gaitou 512 288 0 2
	pl 1 rot 0 0 90
	pl 2 rot 0 0 90
	wait
	pl 1 move 0 0-512 576+144
	pl 2 move 0 0-2560 576+720
	wait
	bg 1 bg15 0 0-288 0 0
	bg 2 bg15_d 0 0+288 0 0
	bg 1 mcarc 900 0 360 0 32 0
	bg 2 mcarc 900 0 360 0 32 0
	wait
	pl 1 blend 255
	pl 2 blend 255
	pl 1 mcmove 200 1024+2560 288-720
	pl 2 mcmove 200 1024+512 288-144
	pl 1 mcscalecos 200 200 200 0% 0% 0% 100% 100% 100%
	pl 2 mcscalecos 200 200 200 100% 100% 100% 0% 0% 0%
	wait

Implement save/load

Save and load is not correct

Use cookies for web/savefile for local
Need to save full state:

Variables
Audio
Choices