Finally getting to a form of the game that has some substance and overcome most of my most serious technical hurdles:
a) WebXR interface: Made all this work although I had a little trouble with the emulators. You can enter the game as an XR session with appropriate hardware - I have look to select so that if you look at an object for a bit it gets clicked with a sweet little torus as UI. I also implemented some rotation controls for the puzzle in the VR world (look down a bit to find them) - they could use some work aesthetically but they're functional. Also you can fast select using triggers or buttons (if your hardware has buttons) and rotate the world using the joysticks (if your hardware has joysticks). I've played through the game with my 'cardboard' headset so I know it can be played with the oldest hardware!
b) Level selection and switching between levels.
So it's beginning to look like a game - here is a demo with 5 levels implemented. I'm not sure these levels will be my final versions we'll see how we go.