HoloLens creator Alex Kipman tried Valve’s upcoming VR title Half-Life: Alyx and shared some choice words about his experience.

Microsoft and Valve have long had close ties, both geographically and historically. Valve was co-founded after two Microsoft employees, Gabe Newell and Mike Harrington, left the company after working on some of the earliest versions of the Windows operating system.

They didn’t go far. Valve’s office—just outside of Seattle—is but a 10 minute drive from Microsoft’s Redmond, WA headquarters. Especially considering their proximity and history, it’s no wonder that at least two Microsoft executives have swung by Valve’s offices to check out their flagship VR title, Half-Life: Alyx, for a glimpse ahead of its release next year.

Alex Kipman, the chief visionary behind HoloLens, had some serious praise to share after trying the game just last week.

“Had the great privilege to play Half-Life: Alyx at Valve yesterday. Most inspiring and immersive VR game I have ever experience and I have played a few,” he shared on Twitter.

While Kipman (who is also closely associated with Microsoft VR projects) is clearly understating the number of VR games he has played as a matter of emphasis, his focus is much more on AR (which is typically not as game-focused) than VR.

On the other hand, Microsoft’s Phil Spencer, Head of Xbox, lives and breathes games. And while he maintains that the company’s next console, Xbox Series X (formerly Project Scarlett), won’t focus on VR, he also got to try Half-Life: Alyx this Summer and called it “amazing.”