VGUI

Valve Graphical User Interface (VGUI) It is an interface library created by Valve Software for use in their Steam distribution client and GoldSrc and Source game engines. VGUI in its present form (used in Steam and Source) is known as VGUI2. VGUI2 has many common graphical controls such as buttons, radio fields, text fields, and allows for the customization and creation of original controls. VGUI is Unicode compliant and platform-independent.