anti-purple-ui（反紫色用户界面）

Anti-Purple UI

This skill enforces a strict monochrome-plus-one-accent color discipline. It exists to eliminate the default AI/SaaS aesthetic: purple gradients, blue-violet glows, teal-to-indigo sweeps, frosted glass with color tints, and multi-hued palettes masquerading as "minimal."

The Rule

Grayscale everywhere. One accent. No exceptions.

The entire UI is built from a neutral grayscale scale. A single accent color — chosen deliberately and used sparingly — provides all contrast and emphasis. Everything else is black, white, or gray.

Color System

Grayscale Scale (CSS variables — always define these)

:root {
  --color-bg:        #0a0a0a;  /* near-black background */
  --color-surface:   #141414;  /* card / panel surface */
  --color-border:    #2a2a2a;  /* subtle dividers */
  --color-muted:     #555555;  /* disabled, placeholder */
  --color-secondary: #888888;  /* secondary text */
  --color-primary:   #e0e0e0;  /* primary text */
  --color-white:     #f5f5f5;  /* headings, high-emphasis */

  /* For light-mode variants, invert the scale: */
  /* --color-bg: #f5f5f5; --color-white: #0a0a0a; etc. */
}

The Accent

Define one accent color. Pick it based on context and intended mood. Do not pick it arbitrarily — the choice should feel intentional.

:root {
  --color-accent: /* ONE color only */;
  --color-accent-dim: /* same hue, lower saturation/lightness for hover states */;
}

Good accent choices by mood:

Forbidden accent choices (these ARE the AI aesthetic):

• ❌ Purple (#7c3aed, #6366f1, #8b5cf6, any violet)
• ❌ Blue-violet, indigo, lavender
• ❌ Teal-to-indigo transitions
• ❌ "Brand blue" (#3b82f6, #2563eb)
• ❌ Pastel anything
• ❌ Multiple accent colors ("just a secondary accent" — no)

Usage Rules

Accent is for emphasis only

The accent appears on:

• The single most important interactive element (primary CTA button)
• Active / selected state indicators
• One key data point or metric that needs to stand out
• Focused input borders
• Progress / loading indicators

The accent does not appear on:

• Backgrounds (other than tiny badges or pills)
• Large surface areas
• Decorative elements
• More than ~10% of total visible UI area

No gradients. Period.

/* ❌ Never */
background: linear-gradient(135deg, #667eea, #764ba2);
background: linear-gradient(to right, var(--color-accent), purple);

/* ✅ Always */
background: var(--color-surface);
border-left: 3px solid var(--color-accent); /* accent as line, not fill */

No color shadows or glows

/* ❌ Never */
box-shadow: 0 0 20px rgba(124, 58, 237, 0.4);
text-shadow: 0 0 10px #7c3aed;

/* ✅ If shadows, always neutral */
box-shadow: 0 4px 16px rgba(0, 0, 0, 0.5);

No frosted glass with tints

/* ❌ Never */
background: rgba(99, 102, 241, 0.1);
backdrop-filter: blur(12px);

/* ✅ If glass effect, neutral only */
background: rgba(255, 255, 255, 0.04);
backdrop-filter: blur(8px);
border: 1px solid var(--color-border);

Contrast & Accessibility

With a monochrome system, contrast must come from value, not hue. Ensure:

• Body text (--color-primary) hits WCAG AA against --color-bg
• Accent color on dark background hits WCAG AA (4.5:1 for text, 3:1 for UI components)
• Don't rely on color alone to communicate state — use icons, labels, or weight changes too

Component Patterns

Buttons

/* Primary — the ONE place accent lives prominently */
.btn-primary {
  background: var(--color-accent);
  color: var(--color-bg);  /* or --color-white depending on accent lightness */
  border: none;
}

/* Secondary — monochrome only */
.btn-secondary {
  background: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-primary);
}
.btn-secondary:hover {
  border-color: var(--color-primary);
}

Cards / Surfaces

.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  /* Optional: accent left-border for featured/highlighted card */
}
.card--featured {
  border-left: 3px solid var(--color-accent);
}

Data / Stats

/* Accent only on the ONE metric that matters most */
.stat-value--primary { color: var(--color-accent); }
.stat-value--secondary { color: var(--color-white); }
.stat-label { color: var(--color-secondary); }

Light Mode Variant

Invert the scale and keep the same accent discipline:

:root[data-theme="light"] {
  --color-bg:        #f8f8f8;
  --color-surface:   #ffffff;
  --color-border:    #e0e0e0;
  --color-muted:     #b0b0b0;
  --color-secondary: #666666;
  --color-primary:   #1a1a1a;
  --color-white:     #0a0a0a;
  /* --color-accent stays the same */
}

Checklist Before Delivering

Before finalizing any UI built under this skill, verify:

• Zero purple, violet, indigo, or teal-to-purple gradients anywhere
• Exactly one accent color defined and used
• Accent covers ≤10% of total visual area
• No colored shadows or glows
• No multi-stop gradients (single-color tints at low opacity are OK on surfaces)
• All interactive states expressed through value/weight changes, not new colors
• Background and surface colors are neutral grays/blacks/whites only
• Frosted glass (if used) has no color tint

Working with frontend-design skill

This skill overrides the color section of frontend-design. Everything else in frontend-design (typography, layout, motion, spatial composition) still applies. When both are active:

1. Read frontend-design for overall creative direction
2. Apply this skill's color system as a strict constraint on top
3. The accent color should be chosen to match the chosen aesthetic tone (e.g., a brutalist layout pairs well with raw red; an editorial layout with ink red or amber)