Playzones
From Mod Wiki
Many aspects of the game (such as deploying and traveling before being warned of leaving the battlefield) take place in the main gameplay area of the map, the 32768 unit square. A typical ETQW map is larger due to an out of bounds area, so actual bounds of a map are a 40960 unit square. Playzone brushes are used to specify the main gameplay bounds of a map. It is on these brushes that a mask is specified. The themselves control where the different aspects of the game may take place.