У вашего броузера проблема в совместимости с HTML5
Mapping for Quake: Advanced Curves Part 1
Award winning Quake mapper Bal shares methods for making advanced curves in TrenchBroom. This is part 1 of 2. NOTE: at 4:34 the graphic for the EXTRUDE function should read: Ctrl+Shift+Left Click+Drag
CZG’s Curve tutorial
http://www.quaketerminus.com/hosted/happymaps/curv_tut.htm
Mapping for Quake on Discord
https://discordapp.com/invite/j5xh8QT
func_msgboard
http://www.celephais.net/board/forum.php
Bal’s episode of the Quakecast
https://quakecast.podbean.com/e/quakecast-4-bal/