Classic CRT Computer Displays

They had rounded corners due to the ray scan was from a single point
and it makes an ellipse.

LCD/LED Displays

• Perfectly rectangular due to pixels are squares
• UI have changed into utilising corners and usually have icons or those kinds of stuff there.

Modern Mobile Displays

• Lots are having rounded corners now
• Fits something about near future of 3D projection below.

Near Future 3D Projection

• Seems to have rounded corners and even blurry rim.
• UI should change to avoid corners.