Which design innovation did Apple make to the original iPod in 2003 that revolutionized its user interface and became a signature feature for future models?

The music industry has seen remarkable product innovations that have transformed how we experience sound. From analog to digital, the evolution of music products has shaped cultural movements and listening habits worldwide. This trivia question focuses on a pivotal product design decision that changed the trajectory of a famous music device. Test your knowledge of music product history!

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The Click Wheel - replacing separate buttons with a touch-sensitive scroll wheel that integrated multiple functions
The Color Screen - introducing the first full-color display on a portable music player
The Dock Connector - creating a proprietary connection format that would last for nearly a decade
Bluetooth Connectivity - making the iPod the first mainstream wireless music device