Whether via Valve’s Steam or Nvidia’s website, you can now download the RTX demo of Quake II that got The Verge’s Sam Byford excited when he tried it at Computex a week ago. RTX is Nvidia’s branding for ray tracing, covering graphics cards, computers, and games that support it, and this Quake recreation is one of the most instantly appealing and accessible manifestations of the tech. You’ll obviously need to have an RTX GPU somewhere in your system in order to make the magic of real-time light and shadow calculations happen, but if you do, the first three levels of Quake II are waiting for you to download and enjoy for free. And if you want the full game, that can be had for $4.99.