Lua API

doukutsu-rs includes a multiplayer-aware and event-based Lua API that lets you customize the behavior of Cave Story in many ways, allowing you to create stunning single and multi-player experiences. It's designed to be engine-agnostic as possible, for ease of implementation in other projects.

The API documentation is generated from TypeScript declarations and is available here.

Scripts

• boot.lua - runs in global context (so every loaded script inherits the global properties set in it). It is executed at game startup before the window is created and is a place where you can override certain settings such as window size and name, data paths and etc. Due to it's nature, it doesn't get reloaded when you use the Reload Scripts debugger option. This is not sandboxed, so you need to be careful on what you expose in it to other scripts. However it lets you load bytecode-based scripts and native extensions which is a very powerful feature (you can e.g., implement Discord rich presence that way) but also may crash the engine if used improperly.

• scripts/*.lua - sandboxed user scripts, note that their loading order isn't guaranteed and they run in separate contexts.

Settings

There are various internal engine-specific settings that can be changed in doukutsu-rs, but many of them are considered out of scope of the common modding API. You can use doukutsu.setSetting(name, value) to modify those settings.

Setting types

Type	Description
int	a signed integer
uint	an unsigned integer
float	a floating point number
string	a string literal
bool	a boolean
"a" | "b"	an enumeration type - only a specified set of values (delimited by | is allowed)

List of settings

Name	Description	Type	Default Value
drs.tsc.encoding	Character encoding used while reading .tsc files	"utf-8" | "shift-jis"	"shift-jis"
drs.tsc.encrypted	If set to true, doukutsu-rs will descramble the .tsc file before reading (in same way as vanilla engine does: grab the byte in halfway of the file (if the file size is not even, round the location towards zero) - if the byte equals 0x00, use 0xf9 instead. Then subtract (with wrapping) that value from every byte in the file, except the byte that was used for descrambling.)	bool	true
drs.window.title	Sets the window title. Works during any event.	string	"Cave Story ~ Doukutsu Monogatari (doukutsu-rs)"
drs.window.width drs.window.height	Sets the default window width/height. Has only an effect on first startup. Works only on platforms that support windowing, has no effect if the game runs exclusively in full screen mode (eg. on Android)	uint	640 480