Which innovative product design feature, introduced in 2007, eliminated physical keyboards on smartphones and fundamentally changed mobile device interfaces forever?

Product design has led to some of history's most revolutionary inventions and discoveries. Behind many world-changing products are fascinating design decisions that balanced form, function, and user experience. This trivia question focuses on a pivotal design choice that transformed how we interact with everyday technology. Test your knowledge about the intersection of innovation and product design in this challenging question!

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Multi-touch capacitive touchscreen technology
QWERTY slide-out keyboard mechanism
Haptic feedback vibration system
Voice command recognition software