Which famous product design was created after its inventor observed people struggling with an existing interface during usability testing?

The world's most innovative products often have fascinating origin stories. From accidental discoveries to purposeful design challenges, the journey from concept to revolutionary product can be surprising. This trivia question explores how one of the most influential product designs in history came to be, revealing the intersection of invention, necessity, and creative problem-solving that led to a design that changed how millions interact with technology.

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The computer mouse, created by Douglas Engelbart after watching users struggle with keyboard-only commands
The iPhone's touchscreen interface, designed after Steve Jobs witnessed people having difficulty with stylus-based smartphones
The QWERTY keyboard layout, developed by Christopher Sholes to slow typists down and prevent typewriter jams
The pull-tab can opener, invented by Ermal Fraze after he forgot a can opener at a picnic