The feature is ported from Better Brightness Slider. 

Better Brightness Slider expands the default brightness slider, making it range from -100% to 1200% (fullbright) instead of 0% to 100%. It's a clientside mod, so it isn't required on servers.

Upgrade version to 1.21+ NeoForge. 

The mod should be compatible with Optifine and Embeddium.

WARN：Version 1.21.3+ is still a testing version, please wait for the update