smart phone

I am seeking ideas, or thoughts, on how to make a cable connected touch pen invisible to the capacitive touch screen of a modern smartphone without mechanically lifting the pen (see illustration). This is for a two axis (no lifting!) planer lego robot I am building to teach machine learning, in...

I have worked on basic low speed PCBs and understand basics of the design methodologies for it. But I am curious about the hi-speed PCBs like smartphone motherboards.. How are the components placed so close to make the PCB compact? How are the tracks routed in this tight spaces? What...