My experience with Linux on laptops is that the default backlight controls are very coarse -
they only work in 10% increments, and a 10% brightness at night is a lot.
The usual suggestion for fixing that is to use xbacklight - if you're trying to do that,
this answer worked for me.
However in my case, specifying the intel driver in xorg.conf broke things,
and this is the result of replacing xbacklight.
The task is simple - read and write the /sys/class/backlight/intel_backlight/brightness file.
While a script could easily do that, it wouldn't allow me to set the SUID bit and would require sudo. So, Rust it was!
xhacklight [=N|+N|-N|inc|dec]
The [=+-]N variants work as expected, but on a scale from 0 to 60000,
which is the native scale of the brightness file - on my system, at least.
inc and dec try to be smart by using a somewhat logarithmic scale:
values are more fine-grained on the darker side, more coarse on the brighter side.
Without arguments, the current brightness as a number between 0 and 60000 is printed.