> Also, you cannot expect a user to operate a vertical touch screen for many hours. Our human upper body isn't built for this Indeed. Back in the days when peo

> Also, you cannot expect a user to operate a vertical touch screen for many hours. Our human upper body isn't built for this Indeed. Back in the days when people thought light pens were cool[1], "gorilla arm" was a common term for the way your body felt after using one for a while. I doubt it matters much whether you're using a pen or your finger, in terms of the fatigue that develops. Ha! Just checked, and "gorilla arm" is still apparently in use. https://www.techopedia.com/definition/31480/gorilla-arm https://www.techopedia.com/definition/31480/gorilla-arm [1] Edit: Some say that what really killed off light pens was company lawyers freaking out over the idea of Junior using a pointy stick on a fragile glass CRT with vacuum inside. Definitely something that could go wrong in a big way.