From: 
Half-Life: Visitors
// Valve Game Info file
// These are key/value pairs. Certain mods will use different settings.
//
gamedir "visitors"
game "Half-Life: Visitors"
startmap "vis01"
trainmap "vis_chillout"
developer_url "http://halflife-visitors.de/en/index.htm"
url_info "www.planethalflife.com/visitors"
url_dl "http://www.planethalflife.com/visitors/en/files.htm"
mpentity "info_player_deathmatch"
gamedll "dlls\hl.dll"
gamedll_linux "dlls/hl.so"
gamedll_osx "dlls/hl.dylib"
cldll "1"
secure "1"
type "singleplayer_only"