1981 document shows why mouse pointer is tilted and not straight

The drawing above shows the concept for the original mouse pointer invented by Douglas Engelbart, with a vertical pointer.

When the graphical user interface was later developed by Xerox, however, the team found that the vertical pointer was almost impossible to see due to the low resolution displays in use at the time.

Rather than make the pointer larger, the decision was made to turn it 45 degrees, making it easy to see. Despite the high resolution displays we have today, the concept has managed to stick for 33 years.

This 1981 document from Xerox’s Palo Alto Research Center describes the new technology involved in the GUI and the optical mouse.