Product register

When design SERVES the product: app UIs, admin dashboards, settings panels, data tables, tools, authenticated surfaces, anything where the user is in a task.

The product slop test

Not "would someone say AI made this." Familiarity is often a feature here. The test is: would a user fluent in the category's best tools (Linear, Figma, Notion, Raycast, Stripe come to mind) sit down and trust this interface, or pause at every subtly-off component?

Product UI's failure mode isn't flatness, it's strangeness without purpose: over-decorated buttons, mismatched form controls, gratuitous motion, display fonts where labels should be, invented affordances for standard tasks. The bar is earned familiarity. The tool should disappear into the task.

Typography

• System fonts are legitimate. -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif gives you native feel on every platform. Inter is the common cross-platform default for a reason.
• One family is often right. Product UIs don't need display/body pairing. A well-tuned sans carries headings, buttons, labels, body, data.
• Fixed rem scale, not fluid. Clamp-sized headings don't serve product UI. Users view at consistent DPI, and a fluid h1 that shrinks in a sidebar looks worse, not better.
• Tighter scale ratio. 1.125–1.2 between steps is typical. More type elements here than on brand surfaces; exaggerated contrast creates noise.
• Line length still applies for prose (65–75ch). Data and compact UI can run denser; tables at 120ch+ are fine.

Color

Product defaults to Restrained. A single surface can earn Committed (a dashboard where one category color carries a report, an onboarding flow with a drenched welcome screen), but Restrained is the floor.

• State-rich semantic vocabulary: hover, focus, active, disabled, selected, loading, error, warning, success, info. Standardize these.
• Accent color used for primary actions, current selection, and state indicators only, not decoration.
• A second neutral layer for sidebars, toolbars, and panels (slightly cooler or warmer than the content surface).

Layout

• Predictable grids. Consistency IS an affordance; users navigate faster when the structure is expected.
• Familiar patterns are features. Standard navigation (top bar, side nav), breadcrumbs, tabs, and form layouts have established user expectations. Don't reinvent for flavor.
• Responsive behavior is structural (collapse sidebar, responsive table, breakpoint-driven columns), not fluid typography.

Components

Every interactive component has: default, hover, focus, active, disabled, loading, error. Don't ship with half of these.

• Skeleton states for loading, not spinners in the middle of content.
• Empty states that teach the interface, not "nothing here."
• Consistent affordances across the surface. Same button shape. Same form-control vocabulary. Same icon style.

Motion

• 150–250 ms on most transitions. Users are in flow; don't make them wait for choreography.
• Motion conveys state, not decoration. State change, feedback, loading, reveal: nothing else.
• No orchestrated page-load sequences. Product loads into a task; users don't want to watch it load.

Product bans (on top of the shared absolute bans)

• Decorative motion that doesn't convey state.
• Inconsistent component vocabulary across screens. If the "save" button looks different in two places, one is wrong.
• Display fonts in UI labels, buttons, data.
• Reinventing standard affordances for flavor (custom scrollbars, weird form controls, non-standard modals).
• Heavy color or full-saturation accents on inactive states.

Product permissions

Product can afford things brand surfaces can't.

• System fonts and familiar sans defaults (Inter, SF Pro, system-ui stacks).
• Standard navigation patterns: top bar + side nav, breadcrumbs, tabs, command palettes.
• Density. Tables with many rows, panels with many labels, dense information when users need it.
• Consistency over surprise. The same visual vocabulary screen to screen is a virtue; delight is saved for moments, not pages.