On a phone, completing a task matters more than fitting a good-looking page on the screen. We check that buttons are easy to tap, menus can be closed, and forms have understandable labels. As a baseline, tap targets are at least 24 by 24 CSS pixels, the minimum set in WCAG 2.2. The on-screen keyboard should not make the active field or necessary next step unreachable. An error message should explain what the visitor needs to change before continuing.
We test the same components with a keyboard, so controls do not rely on touch or a mouse. Focus stays visible and follows a logical order. Floating buttons and banners must not block content when someone zooms in. For unusual interactions, we agree on supported situations and identify existing components that would work better if simplified.