/* ============================================================
   RoofCalc Pro - Design System & Stylesheet
   Inspired by Vercel's design language with warm roofing accents
   ============================================================ */

/* ----- 1. CSS Custom Properties (Design Tokens) ----- */
:root {
  /* Brand Colors */
  --color-ink: #171717;
  --color-on-ink: #ffffff;

  /* Surface Colors */
  --color-canvas: #ffffff;
  --color-canvas-soft: #fafafa;
  --color-canvas-soft-2: #f5f5f5;

  /* Text Colors */
  --color-text: #171717;
  --color-text-secondary: #4d4d4d;
  --color-text-muted: #888888;
  --color-text-on-primary: #ffffff;

  /* Accent - Warm Amber for Roofing Theme */
  --color-accent: #d97706;
  --color-accent-light: #fef3c7;
  --color-accent-dark: #92400e;
  --color-accent-bg: #fffbeb;

  /* Semantic Colors */
  --color-link: #0070f3;
  --color-link-deep: #0761d1;
  --color-success: #059669;
  --color-success-soft: #d1fae5;
  --color-error: #dc2626;
  --color-error-soft: #fee2e2;
  --color-warning: #d97706;
  --color-warning-soft: #fef3c7;

  /* Border Colors */
  --color-hairline: #ebebeb;
  --color-hairline-strong: #a1a1a1;

  /* Border Radius */
  --radius-xs: 4px;
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --radius-pill: 100px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-xs: 0 0 0 1px rgba(0, 0, 0, 0.08);
  --shadow-sm: 0px 1px 1px rgba(0, 0, 0, 0.03), 0px 2px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0px 2px 2px rgba(0, 0, 0, 0.05), 0px 4px 8px -4px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0px 2px 2px rgba(0, 0, 0, 0.04), 0px 8px 16px -4px rgba(0, 0, 0, 0.08);
  --shadow-xl: 0px 1px 1px rgba(0, 0, 0, 0.03), 0px 8px 16px -4px rgba(0, 0, 0, 0.06), 0px 24px 32px -8px rgba(0, 0, 0, 0.1);

  /* Spacing */
  --space-xxs: 4px;
  --space-xs: 8px;
  --space-sm: 12px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 40px;
  --space-3xl: 48px;
  --space-4xl: 64px;
  --space-5xl: 96px;

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, 'SF Mono', Consolas, monospace;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;

  /* Container */
  --container-max: 1200px;
  --container-padding: var(--space-lg);

  /* Header */
  --header-height: 64px;
}

/* ----- 2. Dark Mode Overrides ----- */
[data-theme="dark"] {
  --color-ink: #ffffff;
  --color-on-ink: #171717;

  --color-canvas: #171717;
  --color-canvas-soft: #0a0a0a;
  --color-canvas-soft-2: #1f1f1f;

  --color-text: #f5f5f5;
  --color-text-secondary: #a1a1a1;
  --color-text-muted: #666666;
  --color-text-on-primary: #ffffff;

  --color-accent: #f59e0b;
  --color-accent-light: #78350f;
  --color-accent-dark: #fbbf24;
  --color-accent-bg: #1c1917;

  --color-link: #3b82f6;

  --color-hairline: #2a2a2a;
  --color-hairline-strong: #444444;

  --shadow-xs: 0 0 0 1px rgba(255, 255, 255, 0.06);
  --shadow-sm: 0px 1px 1px rgba(0, 0, 0, 0.2), 0px 2px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0px 2px 2px rgba(0, 0, 0, 0.2), 0px 4px 8px -4px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0px 2px 2px rgba(0, 0, 0, 0.2), 0px 8px 16px -4px rgba(0, 0, 0, 0.3);
  --shadow-xl: 0px 1px 1px rgba(0, 0, 0, 0.2), 0px 8px 16px -4px rgba(0, 0, 0, 0.3), 0px 24px 32px -8px rgba(0, 0, 0, 0.4);
}

/* ----- 3. Reset & Base ----- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-canvas-soft);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color var(--transition-base), color var(--transition-base);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--color-link);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-link-deep);
}

ul {
  list-style: none;
}

/* ----- 4. Typography ----- */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

h1 { font-size: clamp(2rem, 5vw, 3rem); letter-spacing: -0.03em; }
h2 { font-size: clamp(1.5rem, 4vw, 2.25rem); }
h3 { font-size: clamp(1.25rem, 3vw, 1.5rem); }
h4 { font-size: 1.25rem; }

p {
  color: var(--color-text-secondary);
  margin-bottom: var(--space-md);
}

.mono-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 400;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
}

/* ----- 5. Layout ----- */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

/* ----- 6. Header ----- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-height);
  background-color: var(--color-canvas);
  border-bottom: 1px solid var(--color-hairline);
  transition: background-color var(--transition-base), border-color var(--transition-base);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.03em;
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.logo:hover {
  color: var(--color-text);
}

.logo span {
  color: var(--color-accent);
}

.logo-icon {
  width: 28px;
  height: 28px;
  color: var(--color-accent);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.main-nav a {
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: all var(--transition-fast);
}

.main-nav a:hover {
  color: var(--color-text);
  background-color: var(--color-canvas-soft-2);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

/* Buttons in header */
.icon-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-full);
  background: var(--color-canvas);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.icon-btn:hover {
  border-color: var(--color-hairline-strong);
  color: var(--color-text);
  background: var(--color-canvas-soft-2);
}

.icon-btn svg {
  width: 18px;
  height: 18px;
}

/* Mobile menu toggle - hidden on desktop */
.menu-toggle {
  display: none;
}

/* Mobile Nav */
.mobile-nav {
  display: none;
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--color-canvas);
  padding: var(--space-lg);
  z-index: 99;
  flex-direction: column;
  gap: var(--space-sm);
  opacity: 0;
  transform: translateY(-10px);
  pointer-events: none;
  transition: opacity var(--transition-base), transform var(--transition-base);
}

.mobile-nav.active {
  opacity: 1;
  transform: translateY(0);
  pointer-events: all;
}

.mobile-nav a {
  display: block;
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-md);
  font-size: 1.125rem;
  font-weight: 500;
  color: var(--color-text);
}

.mobile-nav a:hover {
  background-color: var(--color-canvas-soft-2);
}

/* ----- 7. Breadcrumbs ----- */
.breadcrumbs {
  padding: var(--space-sm) 0;
  background-color: var(--color-canvas);
  border-bottom: 1px solid var(--color-hairline);
  font-size: 0.8125rem;
}

.breadcrumbs .container {
  display: flex;
  align-items: center;
  gap: var(--space-xxs);
}

.breadcrumbs a {
  color: var(--color-text-muted);
}

.breadcrumbs a:hover {
  color: var(--color-text);
}

.breadcrumbs .separator {
  color: var(--color-text-muted);
  margin: 0 var(--space-xxs);
}

.breadcrumbs .current {
  color: var(--color-text-secondary);
  font-weight: 500;
}

/* ----- 8. Hero Section ----- */
.hero {
  padding: var(--space-4xl) 0 var(--space-3xl);
  background: var(--color-canvas);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% -20%, rgba(217, 119, 6, 0.08) 0%, transparent 60%),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(0, 112, 243, 0.05) 0%, transparent 50%),
    radial-gradient(ellipse 50% 40% at 20% 60%, rgba(217, 119, 6, 0.04) 0%, transparent 50%);
  pointer-events: none;
}

.hero .container {
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xxs);
  padding: var(--space-xxs) var(--space-sm);
  background: var(--color-accent-bg);
  border: 1px solid var(--color-accent-light);
  border-radius: var(--radius-full);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-accent-dark);
  margin-bottom: var(--space-lg);
}

.hero h1 {
  margin-bottom: var(--space-md);
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}

.hero p {
  font-size: 1.125rem;
  max-width: 600px;
  margin: 0 auto var(--space-lg);
  color: var(--color-text-secondary);
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: var(--space-2xl);
  margin-top: var(--space-xl);
  flex-wrap: wrap;
}

.hero-stat {
  text-align: center;
}

.hero-stat-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.hero-stat-label {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ----- 9. Calculator Section ----- */
.calculator-section {
  padding: var(--space-3xl) 0 var(--space-4xl);
}

.calculator-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-xl);
  align-items: start;
}

/* Form Card */
.form-card {
  background: var(--color-canvas);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-md);
  transition: background-color var(--transition-base), border-color var(--transition-base), box-shadow var(--transition-base);
}

.form-card h2 {
  margin-bottom: var(--space-lg);
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.form-card h2 svg {
  width: 24px;
  height: 24px;
  color: var(--color-accent);
}

/* Form Groups */
.form-group {
  margin-bottom: var(--space-lg);
}

.form-label {
  display: block;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-xs);
  letter-spacing: -0.01em;
}

.form-label-hint {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-weight: 400;
}

/* System Toggle */
.system-toggle {
  display: flex;
  background: var(--color-canvas-soft-2);
  border-radius: var(--radius-sm);
  padding: 3px;
  width: fit-content;
  border: 1px solid var(--color-hairline);
}

.system-btn {
  padding: var(--space-xs) var(--space-md);
  border: none;
  border-radius: var(--radius-xs);
  background: transparent;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-muted);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}

.system-btn.active {
  background: var(--color-canvas);
  color: var(--color-text);
  box-shadow: var(--shadow-xs);
}

.system-btn:hover:not(.active) {
  color: var(--color-text-secondary);
}

/* Roof Type Selector */
.roof-type-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-xs);
}

.roof-type-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-xxs);
  padding: var(--space-sm) var(--space-xs);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-md);
  background: var(--color-canvas);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  text-align: center;
}

.roof-type-btn svg {
  width: 28px;
  height: 28px;
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
}

.roof-type-btn:hover {
  border-color: var(--color-hairline-strong);
  color: var(--color-text);
}

.roof-type-btn.active {
  border-color: var(--color-accent);
  background: var(--color-accent-bg);
  color: var(--color-accent-dark);
}

.roof-type-btn.active svg {
  color: var(--color-accent);
}

/* Input Row - two columns */
.input-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-md);
}

/* Form Inputs */
.form-input {
  width: 100%;
  height: 44px;
  padding: 0 var(--space-sm);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-sm);
  background: var(--color-canvas);
  color: var(--color-text);
  font-size: 0.9375rem;
  font-family: var(--font-sans);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  outline: none;
}

.form-input:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(217, 119, 6, 0.1);
}

.form-input::placeholder {
  color: var(--color-text-muted);
}

.form-input.has-error {
  border-color: var(--color-error);
  box-shadow: 0 0 0 3px rgba(220, 38, 38, 0.1);
}

.form-select {
  width: 100%;
  height: 44px;
  padding: 0 var(--space-sm);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-sm);
  background: var(--color-canvas);
  color: var(--color-text);
  font-size: 0.9375rem;
  font-family: var(--font-sans);
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  outline: none;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%23888888' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: 36px;
}

.form-select:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(217, 119, 6, 0.1);
}

/* Custom Pitch Fields (hidden by default) */
.custom-pitch-fields {
  display: none;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-md);
  margin-top: var(--space-sm);
}

.custom-pitch-fields.visible {
  display: grid;
}

/* Waste Options */
.waste-options {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
}

.waste-btn {
  padding: var(--space-xs) var(--space-md);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-pill);
  background: var(--color-canvas);
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}

.waste-btn:hover {
  border-color: var(--color-hairline-strong);
  color: var(--color-text);
}

.waste-btn.active {
  border-color: var(--color-accent);
  background: var(--color-accent-bg);
  color: var(--color-accent-dark);
}

.waste-btn.custom-waste-btn.active {
  border-style: dashed;
}

.custom-waste-input {
  display: none;
  width: 80px;
  height: 32px;
  padding: 0 var(--space-xs);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-sm);
  background: var(--color-canvas);
  color: var(--color-text);
  font-size: 0.8125rem;
  font-family: var(--font-sans);
  text-align: center;
  outline: none;
  transition: border-color var(--transition-fast);
}

.custom-waste-input:focus {
  border-color: var(--color-accent);
}

.custom-waste-input.visible {
  display: inline-block;
}

/* Error Message */
.error-message {
  display: flex;
  align-items: center;
  gap: var(--space-xxs);
  font-size: 0.8125rem;
  color: var(--color-error);
  margin-top: var(--space-xxs);
  min-height: 0;
  overflow: hidden;
  transition: all var(--transition-fast);
}

.error-message.visible {
  margin-top: var(--space-xs);
}

.error-message svg {
  width: 14px;
  height: 14px;
  flex-shrink: 0;
}

/* Calculate Button */
.calculate-btn {
  width: 100%;
  height: 52px;
  border: none;
  border-radius: var(--radius-pill);
  background: var(--color-ink);
  color: var(--color-on-ink);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-base);
  font-family: var(--font-sans);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  position: relative;
  overflow: hidden;
}

.calculate-btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-lg);
}

.calculate-btn:active {
  transform: translateY(0);
}

.calculate-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.calculate-btn svg {
  width: 20px;
  height: 20px;
}

/* Loading Spinner */
.spinner {
  display: none;
  width: 20px;
  height: 20px;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-top-color: white;
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

.calculate-btn.loading .btn-text {
  display: none;
}

.calculate-btn.loading .spinner {
  display: block;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Reset Link */
.reset-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xxs);
  margin-top: var(--space-md);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  cursor: pointer;
  background: none;
  border: none;
  font-family: var(--font-sans);
  transition: color var(--transition-fast);
}

.reset-link:hover {
  color: var(--color-text);
}

.reset-link svg {
  width: 14px;
  height: 14px;
}

/* ----- 10. Results Section ----- */
.results-card {
  background: var(--color-canvas);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-md);
  transition: background-color var(--transition-base), border-color var(--transition-base), box-shadow var(--transition-base);
}

.results-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-lg);
  padding-bottom: var(--space-md);
  border-bottom: 1px solid var(--color-hairline);
}

.results-header h2 {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  margin: 0;
  font-size: 1.25rem;
}

.results-header h2 svg {
  width: 22px;
  height: 22px;
  color: var(--color-accent);
}

.results-actions {
  display: flex;
  gap: var(--space-xs);
}

.results-actions button {
  display: flex;
  align-items: center;
  gap: var(--space-xxs);
  padding: var(--space-xs) var(--space-sm);
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-sm);
  background: var(--color-canvas);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}

.results-actions button:hover {
  border-color: var(--color-hairline-strong);
  color: var(--color-text);
  background: var(--color-canvas-soft-2);
}

.results-actions button svg {
  width: 14px;
  height: 14px;
}

/* Result Grid */
.results-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-md);
}

.result-item {
  padding: var(--space-md);
  background: var(--color-canvas-soft);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-hairline);
  transition: background-color var(--transition-base), border-color var(--transition-base);
}

.result-item.full-width {
  grid-column: 1 / -1;
}

.result-item-label {
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-text-muted);
  margin-bottom: var(--space-xxs);
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.result-item-value {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.03em;
  line-height: 1.1;
}

.result-item-value .result-unit {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-muted);
  letter-spacing: 0;
}

.result-item-sub {
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  margin-top: var(--space-xxs);
}

/* Accent highlight for primary result */
.result-item.primary {
  background: var(--color-accent-bg);
  border-color: var(--color-accent-light);
}

.result-item.primary .result-item-value {
  color: var(--color-accent-dark);
}

/* Calculation Summary */
.calc-summary {
  margin-top: var(--space-lg);
  padding: var(--space-md);
  background: var(--color-canvas-soft-2);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-hairline);
}

.calc-summary h4 {
  font-size: 0.8125rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
  display: flex;
  align-items: center;
  gap: var(--space-xxs);
}

.calc-summary h4 svg {
  width: 16px;
  height: 16px;
}

.calc-summary-step {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-xxs) 0;
  font-size: 0.8125rem;
}

.calc-summary-step + .calc-summary-step {
  border-top: 1px solid var(--color-hairline);
}

.calc-summary-step-label {
  color: var(--color-text-secondary);
}

.calc-summary-step-value {
  font-weight: 600;
  color: var(--color-text);
  font-family: var(--font-mono);
  font-size: 0.75rem;
}

/* Empty State (no results yet) */
.results-empty {
  text-align: center;
  padding: var(--space-3xl) var(--space-lg);
}

.results-empty svg {
  width: 48px;
  height: 48px;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
  opacity: 0.4;
}

.results-empty h3 {
  font-size: 1.125rem;
  color: var(--color-text);
  margin-bottom: var(--space-xs);
}

.results-empty p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  max-width: 300px;
  margin: 0 auto;
}

/* ----- 11. FAQ Section ----- */
.faq-section {
  padding: var(--space-4xl) 0;
  background: var(--color-canvas);
}

.faq-section h2 {
  text-align: center;
  margin-bottom: var(--space-2xl);
}

.faq-list {
  max-width: 720px;
  margin: 0 auto;
}

.faq-item {
  border: 1px solid var(--color-hairline);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-sm);
  overflow: hidden;
  transition: border-color var(--transition-fast);
}

.faq-item:hover {
  border-color: var(--color-hairline-strong);
}

.faq-question {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-md) var(--space-lg);
  background: none;
  border: none;
  cursor: pointer;
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-text);
  text-align: left;
  font-family: var(--font-sans);
  transition: background-color var(--transition-fast);
}

.faq-question:hover {
  background: var(--color-canvas-soft);
}

.faq-question svg {
  width: 18px;
  height: 18px;
  color: var(--color-text-muted);
  transition: transform var(--transition-base);
  flex-shrink: 0;
}

.faq-item.open .faq-question svg {
  transform: rotate(180deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-slow), padding var(--transition-base);
}

.faq-item.open .faq-answer {
  max-height: 300px;
}

.faq-answer-inner {
  padding: 0 var(--space-lg) var(--space-lg);
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

/* ----- 12. Footer ----- */
.site-footer {
  padding: var(--space-4xl) 0 var(--space-xl);
  background: var(--color-canvas);
  border-top: 1px solid var(--color-hairline);
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--space-xl);
  margin-bottom: var(--space-2xl);
}

.footer-brand p {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  margin-top: var(--space-sm);
  max-width: 300px;
}

.footer-col h4 {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-family: var(--font-mono);
}

.footer-col a {
  display: block;
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  padding: var(--space-xxs) 0;
  transition: color var(--transition-fast);
}

.footer-col a:hover {
  color: var(--color-text);
}

.footer-bottom {
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-hairline);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-sm);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

/* ----- 13. Toast Notification ----- */
.toast {
  position: fixed;
  bottom: var(--space-lg);
  right: var(--space-lg);
  padding: var(--space-sm) var(--space-lg);
  background: var(--color-ink);
  color: var(--color-on-ink);
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 500;
  box-shadow: var(--shadow-xl);
  z-index: 200;
  transform: translateY(100px);
  opacity: 0;
  transition: all var(--transition-base);
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.toast.visible {
  transform: translateY(0);
  opacity: 1;
}

.toast svg {
  width: 18px;
  height: 18px;
}

/* ----- 14. Print Styles ----- */
@media print {
  .site-header,
  .breadcrumbs,
  .hero,
  .faq-section,
  .site-footer,
  .results-actions,
  .calculate-btn,
  .reset-link,
  .no-print {
    display: none !important;
  }

  .calculator-grid {
    grid-template-columns: 1fr;
  }

  .form-card {
    break-inside: avoid;
    box-shadow: none;
    border: 1px solid #ddd;
  }

  .results-card {
    break-inside: avoid;
    box-shadow: none;
    border: 1px solid #ddd;
  }

  body {
    background: white;
    font-size: 12px;
  }

  .result-item-value {
    font-size: 1.25rem;
  }
}

/* ----- 15. Responsive - Tablet (768px - 1023px) ----- */
@media (max-width: 1023px) {
  .calculator-grid {
    grid-template-columns: 1fr;
  }

  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-lg);
  }

  .footer-col:first-child {
    grid-column: 1 / -1;
  }
}

/* ----- 16. Responsive - Mobile (< 768px) ----- */
@media (max-width: 767px) {
  :root {
    --container-padding: var(--space-md);
  }

  .main-nav {
    display: none;
  }

  .menu-toggle {
    display: flex;
  }

  .mobile-nav {
    display: flex;
  }

  .hero {
    padding: var(--space-2xl) 0;
  }

  .hero-stats {
    gap: var(--space-lg);
  }

  .calculator-section {
    padding: var(--space-lg) 0;
  }

  .form-card,
  .results-card {
    padding: var(--space-lg);
  }

  .roof-type-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .results-grid {
    grid-template-columns: 1fr;
  }

  .footer-grid {
    grid-template-columns: 1fr;
  }

  .footer-bottom {
    flex-direction: column;
    text-align: center;
  }
}

/* ----- 17. Animations ----- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.animate-fade-in-up {
  animation: fadeInUp 0.5s ease forwards;
}

.animate-fade-in {
  animation: fadeIn 0.3s ease forwards;
}

/* Stagger children animation */
.result-item:nth-child(1) { animation-delay: 0ms; }
.result-item:nth-child(2) { animation-delay: 50ms; }
.result-item:nth-child(3) { animation-delay: 100ms; }
.result-item:nth-child(4) { animation-delay: 150ms; }
.result-item:nth-child(5) { animation-delay: 200ms; }
.result-item:nth-child(6) { animation-delay: 250ms; }
.result-item:nth-child(7) { animation-delay: 300ms; }