Briefle words · UI design
Thumb zone
The lower-middle part of a phone screen that a thumb can reach comfortably while holding the phone in one hand.
Say it to an AI
Mobile food-delivery cart: item rows with quantity steppers, a subtotal, and checkout. Every minus and plus gets at least a 44px touch target, and checkout is a full-width sticky footer CTA showing the total, down in the thumb zone. Nothing important lives in the header.
How an expert would brief the stronger version of “Mobile cart”.
See it
Try it as a puzzle →Cart screen of a food delivery app, shown at phone width.
Why: B's Checkout button sits in the bottom thumb zone; A's is in the top-right corner, the hardest place to reach.
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Room 1 · Essentials
Learn “Thumb zone” in a five-minute lesson