This API is constantly being updated on Github, with a ton more features, bug fixes, and other things. Supported for: 1.21.1 Neo, Forge, Fabric 1.20.1 Forge, Fabric
Refraction API was made for commonly used code between multiple projects & includes many useful methods to make adding features such as cutscenes easier to implement and to make the overall development process easier.
ReConfig—Config system with auto syncing support
Atda—Persistent data storage system
Syncables—Server → Client class syncing capability
Channels—Custom data channels between server and client w/ headers
NamedAPI—Extension of Channels for named API channel schemes
Runnabler—Handler for delayed and ticking runnables on client / server
RefractionEvents—Event system with multiloader support
VoxelUtils—Voxel generation utilities
Particler—Particle wrapper with render and tick manipulation
RAABB—Allows for non-axis aligner boxes with collision
Cutscenes—Customizable cutscenes through code (future command support)
Custom debuggers—Similar to Minecraft's system of debugging, Refraction has custom debug support
Interactions—NPC Interaction handler
Quests—Quest handler system, doesn't offer quest stacking by default (future change)
Server Screens—Full server side control of screens without extra packets including closing, opening and sharing data between client ↔ server
Registrable tracking sounds—Ticking sounds that can be registered on the client and called from the server
Flood Filler—Highly customizable flood filler
Camera shake—Provides a camera shake interface
SyncConfig—Automatic syncing for player joins
Vec3Helper—A lot of vec3 util
RScanner—File scanner given a package
And a lot more, just take a look for yourself, mainly in @helper and @feature dirs :D