Toss-Style Design System Rules

Design Direction

• Build quiet, high-trust product UI with clear hierarchy, generous spacing, and minimal ornament.
• Use one primary accent color and rely on grayscale for most structure.
• Avoid decorative gradients, unnecessary shadows, and competing accent colors.
• Prioritize readability, confidence, and fast scanning over visual novelty.

Typography

• Use a strict type scale with clear roles for page title, section title, body, supporting text, and metadata.
• Use font weight and color before using large size changes.
• Never use pure black text; use a dark grayscale foreground.
• Keep line height comfortable for body copy and tighter for short labels or metrics.
• For metrics, make the number visually dominant and the unit smaller but still legible.

Layout and Rhythm

• Use consistent spacing tokens.
• Keep related content close and unrelated content separated by whitespace.
• Use section rhythm: summary, details, action, and supporting context.
• Align form fields, values, and controls predictably.
• Avoid nested cards and excessive borders.

Cards and Surfaces

• Use cards only for grouped content that needs a surface.
• Keep card radius restrained and consistent.
• Use subtle shadows or borders, not both heavily.
• Keep shadow opacity low and avoid dramatic elevation.
• Do not place important controls in low-contrast decorative surfaces.

Color

• Use the accent color for primary actions, selected state, links, or critical brand moments.
• Use semantic colors for status only: success, warning, error, and information.
• Keep disabled and secondary states in grayscale.
• Ensure status is never communicated by color alone.

Dark Mode

• Rebuild the grayscale scale for dark mode rather than inverting colors.
• Reduce bright accent intensity on dark backgrounds.
• Preserve contrast between surface, border, and foreground layers.
• Test charts, cards, and form controls in both modes.

Accessibility

• Meet WCAG AA contrast for text and controls.
• Provide visible focus states.
• Keep tap targets large enough for touch.
• Use semantic HTML and labels before adding ARIA.
• Respect reduced motion preferences.

Common Mistakes

• Do not create one-off spacing values.
• Do not mix multiple unrelated accent colors.
• Do not overuse cards to separate every piece of content.
• Do not rely on large hero typography inside dense product screens.