I could do that with a touchscreen if I didn't need to look at it to know what was where. There's two problems with this. Firstly it's generally unknowable wha

I could do that with a touchscreen if I didn't need to look at it to know what was where. There's two problems with this. Firstly it's generally unknowable what will appear where on the touschreen. Secondly even if you just want to know exactly where the touchscreen is then you need to look at it.