Ray tracing isn’t the easiest of technologies to explain if you don’t have a monster PC right in front of you, and even if you do, game support is currently limited and hugely taxing at high resolutions. Not everyone has the luxury of being able to manipulate a detailed environment in real time and see how its lighting realistically interacts with every object in the scene, which is the ultimate end goal.

Fortunately, the tech turns out to be just as cool when applied to 22-year-old first-person shooters — and in some ways, cooler. Id Software’s mega-hit Quake II was modified to run with ray tracing earlier this year by Christoph Schied, and now Nvidia is releasing the project as Quake II RTX. I just played it for a while at Nvidia’s Taipei headquarters and came away really impressed.

Quake II is a very simple game by today’s graphical standards, which makes the extraordinary visual effects in Quake II RTX stand out even more. Things like the subtle falloff of light streaming through a window or the reflections on a weapon have an uncannily realistic effect that clearly wouldn’t have been possible to render in real time just a few years ago, never mind 1997.

To be clear, it’s not just ray tracing that converts the game into a visual stunner: it has new textures, gun models, and so on. But most of the assets are the same, and it’s obviously still Quake II — just a bizarre dreamland version of Quake II with mathematically accurate lighting.

The ray tracing implementation is arguably more complete than most recent high-profile games that support Nvidia’s RTX-series GPUs, because they tend to focus on a single element such as shadows or reflections. Everything feels consistent with Quake II RTX, and it’s also a lot easier to run it at high resolutions and frame rates.

Nvidia is releasing the first three levels of Quake II RTX for free, shareware-style, on June 6th, and the full game will be available to anyone with a copy of Quake II. Right now that costs $4.99 on Steam. You will, however, need an RTX GPU from Nvidia to run it.