Adapt Native

1. Source context: what was it designed for, and what assumptions did it make? (Phone-only? Portrait-only? One platform’s idioms? A website?)
2. Target context: which device class (phone, tablet, foldable), orientation, platform, and usage posture (one-handed on the go vs two-handed at rest)?
3. What breaks: navigation that doesn’t fit the target, layouts that stretch instead of restructure, gestures or controls that don’t exist there?

Adaptation Strategies

Phone → Tablet (iPad / large screens)

• Restructure, don’t stretch. A scaled-up phone UI on a tablet is the failure mode. Use size classes (iOS) / window size classes (Android) to switch structure.
• Navigation changes shape: tab bar stays or becomes a sidebar on iPad; Android navigation bar becomes a rail or drawer on expanded width.
• Use the width: split view / master-detail (list + detail side by side), multi-column grids, popovers where phones used sheets.
• Multitasking is a size, not an edge case: iPad Split View and Android multi-window can hand you a phone-width window on a tablet; size-class-driven layout handles both for free.

Orientation & foldables

• Landscape restructures (side-by-side panes, repositioned controls); never clip or letterbox. Lock orientation only when the task truly demands it.
• Foldables (Android): react to posture and hinge via window size classes; test folded, unfolded, and tabletop.

Platform → platform (iOS ↔ Android)

Translate idioms; never transplant them:

Rebuild navigation and controls in the target’s vocabulary; carry over the brand’s expressive layer (palette intent, type accent, motion personality) through the target’s theming system.

Web → native (porting a website or web app)

Reconform, don’t reflow. Replace web navigation with the platform’s model, HTML-shaped controls with platform controls, hover affordances with touch-first ones, and px-based type with Dynamic Type / sp. Then treat the result to the full platform reference; the slop test there is the acceptance bar.

Implement & Verify

• Drive structure from size classes / window size classes, never from device-model checks.
• Respect safe areas and window insets in every new configuration (notch, hinge, status bar, keyboard).
• Test on simulators for breadth, then real hardware for truth: at least one phone and one tablet per shipped platform, both orientations, split-screen where supported.

When the adaptation feels native to each context, hand off to /impeccable polish for the final pass.

NEVER:

• Ship a stretched phone layout on a tablet
• Port one platform’s controls or navigation onto the other
• Hide core functionality on smaller devices (if it matters, make it work)
• Lock orientation to dodge a layout bug
• Trust simulators alone (posture, gestures, and performance need hardware)