What is sunreactor?

SunReactor is a small background program, written in Rust, that automatically adjusts your monitor brightness throughout the day. Instead of using a fixed schedule like dimming the screen at 8 PM every night, it calculates the sun's position in the sky based on your city's location and the current date. As the sun rises and sets, your screen brightness smoothly follows along, so it stays in sync even as daylight hours shift with the seasons. If you connect more than one monitor, SunReactor treats each one separately. A laptop screen and an external monitor do not look the same at the same brightness percentage, so you can set different minimum, maximum, and curve settings for each display. You can also give it a free OpenWeather API key, and it will slightly dim your screens on cloudy days using real weather data, on top of the base sun calculation. Under the hood, SunReactor runs as a simple background service on Linux, controlling your screen through existing tools like ddcutil for external monitors and brightnessctl for laptop panels. It does not need administrator or root access, and it runs quietly without an internet connection except for the optional weather feature. It also has its own screen dimming for when your computer sits idle, so you can turn off your desktop's built in power management to avoid conflicts. You interact with SunReactor through a terminal based interface (a TUI), not a graphical app. From there you can pick your city, tune the brightness curve for each monitor, and check current weather conditions. Setup uses an installer script that downloads a pre built version for Linux, checks it before installing, and can be reversed with an uninstall command. You can also build it yourself from source if you have Rust installed. This tool is aimed at Linux users who want their screen brightness to feel more natural across the day without manually adjusting it, particularly people who already use a terminal regularly.