A true 320 CSS-pixel browser viewport for checking every FG UI component, Laboratory condition and real website test as a narrow mobile screen.
The test frame loads the real pages and the exact live /dev/assets/css/fgui.css and /dev/assets/js/fgui.js. No helper CSS or JavaScript is used to repair mobile behaviour.
Scroll inside the phone viewport. Start with All 346 components, then load any other page from the test controls.
Use the frame as a visual release check, not just a resize preview.
Look for clipped content, accidental horizontal scrolling, off-screen menus, tables that do not use their intended scroll container, and components wider than the screen.
Check labels, headings, body text, metadata, icons, rows, cards and stacked controls for cramped or excessive spacing.
Check buttons, menus, selectors, steppers, close controls, pagination, tabs and other interactive targets for comfortable mobile use.
Look for headings that break badly, long labels, code, prices, metadata and action text that collide or overflow.
Open dropdowns, drawers, modals, accordions, date controls and other interactive states while the frame remains at 320px.
Use the five website links as the final check that components still compose cleanly into full mobile pages.