I have reproduced this in the current Nightly. Disabling WebVR with dom.vr.enabled allows it to run normally on Nightly. We are hitting a code path on the site unique to having the WebVR API available, but no HMDs attached. Perhaps the issue could be solved by updating webvr-manager.js and/or the threejs vreffect.js on the site?
I filed a bug on the game's GitHub repo: https://github.com/dlittle42/machinecode/issues/1
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