У вашего броузера проблема в совместимости с HTML5
**UPDATE: I forgot to mentioned the "false floor" in this video is a func_illusionary*** kind of an important point. Also note this is not the only method of solving the issue. Read the comments below for more ideas.
A common problem can be easily fixed with this lighting hack.
Find Quake mapping help and fellowship here:
Mapping for Quake on Discord
https://discordapp.com/invite/j5xh8QT
Grab the map used in this video here:
http://www.quaketastic.com/files/misc/pitch_black_monster_fix_example.zip