From Valve Developer Community
From: 
Half-Life: Sum
// Valve Game Info file
// These are key/value pairs. Certain mods will use different settings.
//
game "Half-Life: Sum"
startmap "sum1"
gamedll "dlls/hl.dll"
gamedll_linux "dlls/hl.so"
gamedll_osx "dlls/hl.dylib"
type "singleplayer_only"
cldll "1"
gamedir "sum"
version "1.0"
icon "sum"
edicts "1500"
