Counterclockwise: the touchscreen evolution

The human-computer interface has been a problem since the dawn of computers. As far as smartphones are concerned, the clear winner is the touchscreen. But how did we get here? The proto-touchscreen was the light pen, which was first developed in the 50s and 60s and was available to consumers as an accessory for 8-bit computers in the 80s. The light pen is a simple but clever solution that works only with CRT monitors - it senses the electron beam as it scans across the phosphor drawing the image line by line, pixel by pixel.