The core rule of mobile UX: the "Thumb Zone" — the bottom of the screen is comfortable with one hand, the top is hard to reach. So primary actions go at the bottom. Minimal taps: users should reach their goal in fewer than 3 taps.
Touch target size should be at least 44×44 pt (iOS) or 48×48 dp (Android) — enough space for a finger. Gestures (swipe, pinch, long press) make an app feel intuitive. Loading states, skeleton screens, and micro-animations make wait times feel shorter.
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