/* Precision Glazing System — Modern Light Theme */
@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700;800&family=Inter:wght@400;500;600;700&display=swap');

:root {
  /* Colors — Clean Light */
  --surface: #f8f9fb;
  --surface-card: #ffffff;
  --surface-alt: #f1f3f7;
  --on-surface: #1a1d26;
  --on-surface-variant: #5a6070;

  --primary: #3563e9;
  --primary-hover: #2a4fd6;
  --on-primary: #ffffff;
  --primary-soft: rgba(53, 99, 233, 0.08);
  --primary-glow: rgba(53, 99, 233, 0.12);

  --secondary: #7b8499;
  --border: #e2e5eb;
  --border-focus: #3563e9;
  --text-muted: #8d95a5;
  --computed-bg: #f1f3f7;

  /* Typography */
  --font-headline: 'DM Sans', system-ui, sans-serif;
  --font-body: 'Inter', system-ui, sans-serif;

  /* Spacing & Sizes */
  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
  --spacing-2xl: 48px;

  /* Shadows */
  --shadow-xs: 0 1px 2px rgba(0,0,0,0.04);
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.05);
  --shadow-card: 0 4px 24px rgba(0,0,0,0.06), 0 1px 3px rgba(0,0,0,0.04);
  --shadow-elevated: 0 12px 40px rgba(0,0,0,0.08), 0 2px 6px rgba(0,0,0,0.03);
}

/* ============ BASE ============ */
* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: var(--font-body);
  background-color: var(--surface);
  color: var(--on-surface);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-headline);
  font-weight: 700;
  color: var(--on-surface);
  margin-bottom: var(--spacing-sm);
  letter-spacing: -0.02em;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.container {
  max-width: 1060px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

/* ============ HERO ============ */
.hero {
  background: linear-gradient(165deg, #eef2ff 0%, #f8f9fb 50%, #e8f0fe 100%);
  padding: 80px 0 130px;
  text-align: center;
  position: relative;
  border-bottom: 1px solid var(--border);
}

.hero::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background:
    radial-gradient(circle at 20% 80%, rgba(53, 99, 233, 0.06) 0%, transparent 50%),
    radial-gradient(circle at 80% 20%, rgba(99, 102, 241, 0.05) 0%, transparent 50%);
  pointer-events: none;
}

.hero h1 {
  font-size: clamp(2.2rem, 5.5vw, 3.5rem);
  font-weight: 800;
  letter-spacing: -0.035em;
  margin-bottom: var(--spacing-md);
  color: var(--on-surface);
  position: relative;
}

.hero p {
  color: var(--on-surface-variant);
  font-size: 1.15rem;
  max-width: 580px;
  margin: 0 auto;
  font-weight: 400;
  line-height: 1.65;
  position: relative;
}

/* ============ CALCULATOR CARD (GRID) ============ */
.calculator-card {
  display: grid;
  grid-template-columns: 1fr 380px;
  background: var(--surface-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-elevated);
  margin-top: -72px;
  margin-bottom: 72px;
  position: relative;
  z-index: 10;
  overflow: hidden;
}

/* Left side inputs */
.calc-inputs {
  border-right: 1px solid var(--border);
}

/* Right side results */
.calc-results {
  background: var(--surface-alt);
  display: flex;
  flex-direction: column;
}

/* ============ COLLAPSIBLE SECTIONS ============ */
.calc-section {
  border-bottom: 1px solid var(--border);
}

.calc-section:last-of-type {
  border-bottom: none;
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-lg) var(--spacing-xl);
  cursor: pointer;
  user-select: none;
  transition: background 0.2s ease;
}

.section-header:hover {
  background-color: var(--primary-soft);
}

.section-header h3 {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--on-surface);
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.section-header h3::before {
  content: '';
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--primary);
  display: inline-block;
}

.chevron-icon {
  width: 20px;
  height: 20px;
  color: var(--secondary);
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.chevron-icon.rotated {
  transform: rotate(180deg);
}

.section-content {
  padding: 0 var(--spacing-xl) var(--spacing-xl);
  overflow: hidden;
  transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1), padding 0.4s ease, opacity 0.3s ease;
  max-height: 2000px;
  opacity: 1;
}

.section-content.collapsed {
  max-height: 0;
  padding-top: 0;
  padding-bottom: 0;
  opacity: 0;
}

/* ============ FORM FIELDS ============ */
.input-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: var(--spacing-lg);
}

.input-group:first-child {
  margin-top: 0;
}

.input-group label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--on-surface-variant);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.input-control {
  height: 48px;
  padding: 0 var(--spacing-md);
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font-body);
  font-size: 0.95rem;
  color: var(--on-surface);
  transition: all 0.2s ease;
}

.input-control:focus {
  outline: none;
  background-color: #fff;
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

.input-control.computed {
  background-color: var(--computed-bg);
  color: var(--primary);
  font-weight: 600;
  cursor: default;
  border-style: dashed;
}

select.input-control {
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%235a6070' viewBox='0 0 16 16'%3E%3Cpath d='M7.247 11.14 2.451 5.658C1.885 5.013 2.345 4 3.204 4h9.592a1 1 0 0 1 .753 1.659l-4.796 5.48a1 1 0 0 1-1.506 0z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 14px center;
  padding-right: 36px;
}

/* Dimension Input (number + unit select) */
.dimension-input {
  display: flex;
  border-radius: var(--radius-sm);
  overflow: hidden;
  border: 1px solid var(--border);
  background-color: var(--surface);
  transition: all 0.2s ease;
}

.dimension-input:focus-within {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

.dimension-input .input-control {
  box-shadow: none;
  border: none;
  background: transparent;
  border-radius: 0;
}

.dimension-input input {
  flex: 1;
  min-width: 0;
}

.dimension-input select {
  width: 88px;
  flex-shrink: 0;
  border-left: 1px solid var(--border);
  background-color: var(--surface-alt);
  color: var(--primary);
  font-weight: 600;
  font-size: 0.85rem;
}

.dimension-input select:hover {
  background-color: #e8ecf5;
}

/* ============ SHAPE DIAGRAM ============ */
.shape-diagram-container {
  padding: var(--spacing-xl);
  flex-grow: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}

.shape-diagram {
  background: var(--surface-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
  height: 100%;
  min-height: 250px;
  box-shadow: var(--shadow-xs);
}

.shape-diagram img {
  max-width: 100%;
  max-height: 240px;
  object-fit: contain;
  transition: transform 0.4s ease, opacity 0.4s ease;
}

/* ============ RESULT AREA ============ */
.result-area {
  background: linear-gradient(180deg, var(--primary-soft) 0%, #ffffff 100%);
  border-top: 1px solid var(--border);
  padding: var(--spacing-xl);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  gap: var(--spacing-md);
}

.result-area .result-label {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 4px;
}

.result-area .result-value {
  font-size: clamp(2.2rem, 5vw, 3.2rem);
  font-weight: 800;
  font-family: var(--font-headline);
  line-height: 1.1;
  color: var(--on-surface);
  word-break: break-word;
  letter-spacing: -0.03em;
}

.result-area .unit-toggle {
  margin-top: 8px;
  background: var(--surface-card);
  border: 1px solid var(--border);
  color: var(--on-surface-variant);
  padding: 8px 24px;
  border-radius: 100px;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.82rem;
  font-family: var(--font-body);
  transition: all 0.2s;
  box-shadow: var(--shadow-xs);
}

.result-area .unit-toggle:hover {
  background: var(--primary);
  color: var(--on-primary);
  border-color: var(--primary);
  box-shadow: var(--shadow-sm);
}

/* ============ EDUCATIONAL CONTENT ============ */
.educational-content {
  margin-bottom: 80px;
}

.content-block {
  margin-bottom: 40px;
  background: var(--surface-card);
  padding: var(--spacing-2xl);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-card);
}

.content-block h2 {
  font-size: 1.75rem;
  margin-bottom: var(--spacing-lg);
  color: var(--on-surface);
  padding-bottom: var(--spacing-md);
  border-bottom: 2px solid var(--primary-soft);
}

.content-block h3 {
  font-size: 1.15rem;
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-sm);
  color: var(--primary);
}

.content-block > p,
.content-block li {
  color: var(--on-surface-variant);
  margin-bottom: var(--spacing-md);
  font-size: 1.02rem;
  line-height: 1.85;
}

.content-block ul,
.content-block ol {
  padding-left: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
}

.content-block ul li {
  margin-bottom: var(--spacing-sm);
  line-height: 1.75;
}

.content-block ol {
  padding-left: 0;
  list-style-type: none;
}

.content-block ol li {
  margin-bottom: var(--spacing-lg);
  padding-left: var(--spacing-lg);
  border-left: 3px solid var(--primary-soft);
}

.content-block code {
  background: var(--surface-alt);
  padding: 4px 10px;
  border-radius: 6px;
  font-size: 0.92rem;
  color: var(--primary);
  border: 1px solid var(--border);
}

.formula {
  background: var(--surface-alt);
  padding: var(--spacing-md) var(--spacing-lg);
  border-radius: var(--radius-md);
  font-family: 'Inter', monospace;
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--primary);
  border: 1px solid var(--border);
  display: inline-block;
  margin: var(--spacing-sm) 0 var(--spacing-md) 0;
}

.uniqueness-addition {
  border-left: 4px solid var(--primary);
}

/* ============ TABLE ============ */
table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  margin-top: var(--spacing-lg);
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  overflow: hidden;
  background: var(--surface-card);
}

th, td {
  padding: 14px 20px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

th {
  background-color: var(--surface-alt);
  font-weight: 700;
  color: var(--on-surface);
  text-transform: uppercase;
  font-size: 0.75rem;
  letter-spacing: 0.06em;
}

td {
  color: var(--on-surface-variant);
  font-size: 0.95rem;
}

tbody tr:last-child td { border-bottom: none; }
tbody tr { transition: background-color 0.15s ease; }
tbody tr:hover { background-color: var(--primary-soft); }

/* ============ FAQ ============ */
.faq-section {
  background: transparent;
  border: none;
  box-shadow: none;
  padding: 0;
}

.faq-section > h2 {
  padding-bottom: var(--spacing-md);
  border-bottom: 2px solid var(--primary-soft);
  margin-bottom: var(--spacing-lg);
}

.faq-item {
  background: var(--surface-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg) var(--spacing-xl);
  margin-bottom: var(--spacing-md);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.faq-item:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-card);
}

.faq-item:last-child { margin-bottom: 0; }

.faq-item h3 {
  margin: 0 0 var(--spacing-sm) 0;
  font-size: 1.08rem;
  color: var(--on-surface);
}

.faq-item p {
  color: var(--on-surface-variant);
  margin: 0;
  font-size: 0.98rem;
  line-height: 1.75;
}

/* ============ CTA BLOCK ============ */
.cta-block {
  background: linear-gradient(135deg, #eef2ff, #e8f0fe) !important;
  border: 1px solid var(--primary-glow) !important;
}

.cta-block h2 {
  border-bottom: none !important;
  color: var(--on-surface);
}

/* ============ FOOTER ============ */
footer {
  border-top: 1px solid var(--border);
  background: var(--surface-card);
  color: var(--text-muted);
  text-align: center;
  padding: var(--spacing-xl);
  font-size: 0.88rem;
}

/* ============ RESPONSIVE ============ */
@media (max-width: 850px) {
  .calculator-card {
    grid-template-columns: 1fr;
  }

  .calc-inputs {
    border-right: none;
    border-bottom: 1px solid var(--border);
  }

  .shape-diagram-container {
    padding: var(--spacing-lg);
  }

  .result-area {
    padding: var(--spacing-lg);
  }
}

@media (max-width: 600px) {
  .hero {
    padding: 56px 0 100px;
  }

  .calculator-card {
    margin-left: -8px;
    margin-right: -8px;
    border-radius: var(--radius-md);
  }

  .section-header {
    padding: var(--spacing-md) var(--spacing-lg);
  }

  .section-content {
    padding-left: var(--spacing-lg);
    padding-right: var(--spacing-lg);
  }

  .content-block {
    padding: var(--spacing-lg);
  }

  .content-block h2 {
    font-size: 1.4rem;
  }
}

/* Global Navigation */
.global-nav {
  background: white;
  border-bottom: 1px solid #e2e8f0;
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 100;
}
.global-nav .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
.global-nav .nav-logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: #0f172a;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.global-nav .nav-links {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  align-items: center;
}
.nav-dropdown {
  position: relative;
  display: inline-block;
}
.nav-dropbtn {
  background: none;
  border: none;
  color: #475569;
  font-size: 0.95rem;
  font-family: inherit;
  font-weight: 500;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 8px 12px;
  border-radius: 6px;
  transition: all 0.2s;
}
.nav-dropbtn:hover {
  color: var(--primary);
  background-color: #f8f9fb;
}
.nav-dropdown-content {
  display: none;
  position: absolute;
  background-color: #fff;
  min-width: 220px;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.1);
  border: 1px solid var(--border);
  border-radius: 8px;
  z-index: 100;
  top: 100%;
  left: 0;
  overflow: hidden;
}
.nav-dropdown-content a {
  color: var(--on-surface);
  padding: 12px 16px;
  text-decoration: none;
  display: block;
  font-size: 0.92rem;
  font-weight: 500;
  transition: all 0.2s;
}
.nav-dropdown-content a:hover {
  background-color: #f1f5f9;
  color: var(--primary);
}
.nav-dropdown:hover .nav-dropdown-content {
  display: block;
}

/* --- CRITICAL MOBILE FIXES --- */
img {
  max-width: 100%;
  height: auto;
}

table {
  display: block;
  overflow-x: auto;
  white-space: nowrap;
  -webkit-overflow-scrolling: touch;
}

.formula {
  white-space: normal;
  word-wrap: break-word;
  max-width: 100%;
}

@media (max-width: 850px) {
  /* Fix Global Nav Stacking */
  .global-nav .container {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }
  .global-nav .nav-logo {
    font-size: 1.15rem;
  }
  .global-nav .nav-links {
    width: 100%;
    flex-wrap: nowrap;
    overflow-x: auto;
    padding-bottom: 4px;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none; /* Firefox */
  }
  .global-nav .nav-links::-webkit-scrollbar {
    display: none; /* Chrome/Safari */
  }
  .nav-dropbtn {
    white-space: nowrap;
    background: var(--surface-alt);
    border-radius: 100px;
    padding: 6px 14px;
    font-size: 0.9rem;
  }
  
  /* Fix Card Placement */
  .hero {
    padding: 40px 0 80px;
  }
  .calculator-card {
    margin-top: -40px;
  }
  
  /* Make dropdowns relative in scroll view or handle them better */
  /* Actually, on mobile, if they tap, the dropdown will appear. 
     Since nav-links is overflow-x: auto, absolute dropdown might get clipped.
     Let's make dropdown content fixed or adjust it. */
  .nav-dropdown-content {
    position: fixed;
    top: auto;
    left: 1rem;
    right: 1rem;
    min-width: auto;
    margin-top: 0.5rem;
  }
}