My exercise bike can play Doom on its display in theory.

Theory doesn't matter here, tooling and standards do. And PDF doesn't just have the tooling for highlighting and annotations, it has the standards for them so that tools support them in an interoperable way. A highlight made with one tool can be removed with another, without altering the underlying content.

I would love an exercise bike that runs doom. Maybe link my movement speed in-game to how fast I pedal, with a joystick on one of the handlebars to move and a couple buttons on the other one to shoot and reload. So far every exercise bike game is just bike race, which I'll admit is a close fit for the existing hardware and probably the first idea I'd have too but it gets boring after a while.

Had the same idea - not with doom - but with a Quest 3D and watching videos of me riding in the summer. First make a film using an 3D camera (something like a Insta360) and then view that on the Quest in winter while riding exercise bike.

Video speed would sync to the exercise bike speed, giving a feeling of reality.

The core problem is that sweating inside a Quest isn't a good idea ...

I did thrill of the fight a lot back during the pandemic. sweating in a quest isn't ideal, but it's not unmanageable for brief periods of time (15-30 minutes). The only real problem is that the lenses can get sweaty or foggy and all of a sudden I go from punching faces and dodging fists to punching at blurs and failing to dodge other blurs.

Maybe instead of a quest you just display video to a screen? When I was using a hotel fitness center they had a peloton and that seems to be something you can do with those. It was a couple years back and I recall the video being loosely if at all tied to the speed you pedal at, but it was more fun than just looking at a wall while I pretend to go somewhere.

It’s a credible argument, but to be clear one I didn’t comment on. It’s the logical next question if I’m correct, which I am.