Gammy is a tool for adjusting pixel brightness/temperature automatically or manually. It can dim the screen if its content is too bright, or brighten it otherwise. This can help your eyes adjust when switching between dark and light windows, especially at night or in suboptimal lighting conditions.
Disclaimer: I do not own this application or tool. I'm just here to share it, but you're free to support the developer. The tool/application's working capability and other issues depend on keeping the project alive by the author. Use it at your own risk.