Screen just went too dim to read (but I can barely see it’s still there).

I have a Razer Blade Stealth (several years old), and while working today, the screen suddenly looked like it shut off.  But on closer examination, it was just extremely dim. Tried ctrl-alt-del twice to try to reboot, but no help. Tried holding down Pwr button for 10 sec, but again unsuccessful. Couldn’t quite see well enough to do normal power right click and scroll to power off. Tried Fn keys for screen brightness with no noticeable effect. Not sure what to try now.