Source 2

Valve currently uses the Source 2 engine to power its biggest modern titles, including Dota 2, Half-Life: Alyx, and Counter-Strike 2. The engine is specifically designed to handle complex physics, high-fidelity textures, and advanced VR rendering, as seen in Half-Life: Alyx. Valve has also slowly ported older titles over to Source 2 to modernize their infrastructure.

While Valve has made elements of Source 2 available through tools like the Dota 2 Workshop Tools, there is no standalone, commercial version of the engine available for general public development. Valve essentially keeps the engine in-house for its own first-party titles and community modding within their specific games. They prioritize internal use over licensing it out to competing studios.

Valve officially announced the Source 2 engine at the Game Developers Conference (GDC) in March 2015. Alongside the announcement, Valve confirmed that Dota 2 would be the first game completely ported over to the new engine. The engine promised a massive overhaul to the physics, audio, and rendering capabilities compared to the original Source engine.

Panorama is the user interface framework utilized by the Source 2 engine, heavily replacing the old Scaleform (Flash-based) UI used in Source 1. It allows developers to build complex, responsive, and highly customizable menus using modern web technologies like HTML, CSS, and JavaScript. Dota 2's intricate shop and HUD are completely built using Panorama.