How to change brightness on puppy linux?

I just installed puppy linux but the screen is literally burning my eyes. The Fn+Brightness key on my laptp doesn't work. I tried to go to setup and change the gamma but it just make the colors darker, the screen itself keeps being extremly bright so I think it's due to the backlight. How can I diminish the backlight or the thing that keeps the screen bright despite me lowering gamma ? **Edit:** in fact when I'm in command prompt mode (GUI closed) the screen is still very bright. Is there a way to fix that too ? **Edit:** I managed to add acpi_backlight=vendor in GRUB as you can find on the internet to fix this problem but this doesn't change anything. Pressing Fn+Arrow still doesn't work and changing the brightness file in acpi_video doesn't work either.