Valve before Half-Life was a dark place full of thick plastic and Quake.
Reddit user Smar_tass has posted up some photos from a trip his dad took to Valve in 1998, showing a bootstrap, cave-like environment where people bought in pizza and fiddled with CRTs.
It appears "light" was something Valve employees didn't value at the time, with the company taking a dim view on anything other than dimness in general.
This is before the release of Half-Life, apparently, which launched in November 1998.
You can check out the full set on Imgur.