A phone is not a smaller desktop.
Mobile journeys have their own rhythm, priorities and touch constraints. Content remains complete while layout becomes natural.
The first screen
The heading, key information and next action need a clear sequence without overlap or accidental horizontal scrolling.
Touch and keyboard
Controls receive enough space, a visible focus state and a logical order. Forms stay readable when the keyboard opens.
Real devices
Emulation is a start. Critical pages are checked across widths and, where relevant, slower network conditions.