:root {
  /* Backgrounds */
  --bg: #f4f8fc;
  --bg-soft: #eef4fb;
  --surface: #ffffff;
  --surface-alt: #f7fbff;

  /* Borders */
  --border: #d8e3ee;
  --border-strong: #c5d3e0;

  /* Text */
  --text: #0f172a;        /* slightly stronger for contrast */
  --text-soft: #475569;
  --text-muted: #64748b;

  /* Primary (Teal) */
  --primary: #0d9488;
  --primary-dark: #0f766e;
  --primary-soft: #ccfbf1;
  --primary-soft-2: #e6fffa;

  /* Secondary (Navy / Structure) */
  --secondary: #1e293b;
  --secondary-soft: #334155;

  /* Accent (Blue interaction tone) */
  --accent: #1e3a8a;

  /* Tertiary (Orange / CTA) */
  --tertiary: #f97316;
  --tertiary-dark: #ea580c;
  --tertiary-soft: #ffedd5;

  /* Feedback */
  --success: #059669;
  --error: #dc2626;

  /* Effects */
  --shadow: 0 12px 30px rgba(15, 23, 42, 0.08);
  --shadow-soft: 0 6px 18px rgba(15, 23, 42, 0.05);

  /* Layout */
  --radius-sm: 10px;
  --radius: 16px;
  --radius-lg: 22px;
  --max-width: 1180px;

  /* Tag Colors */ 
  --tag-airflow-bg: var(--primary-soft);
  --tag-airflow-text: var(--primary-dark);
  --tag-airflow-border: var(--primary);

  --tag-duct-bg: var(--surface-alt);
  --tag-duct-text: var(--secondary-soft);
  --tag-duct-border: var(--border-strong);

  --tag-load-bg: rgba(249, 115, 22, 0.1);
  --tag-load-text: var(--tertiary-dark);
  --tag-load-border: rgba(249, 115, 22, 0.35);

  --tag-pressure-bg: rgba(124, 58, 237, 0.1);
  --tag-pressure-text: #7c3aed;
  --tag-pressure-border: rgba(124, 58, 237, 0.3);

  --tag-slope-bg: rgba(101, 163, 13, 0.1);
  --tag-slope-text: #65a30d;
  --tag-slope-border: rgba(101, 163, 13, 0.35);

  --tag-conversion-bg: rgba(100, 116, 139, 0.1);
  --tag-conversion-text: #64748b;
  --tag-conversion-border: rgba(100, 116, 139, 0.3);

  --tag-hvac-bg: rgba(6, 182, 212, 0.1);
  --tag-hvac-text: #0891b2;
  --tag-hvac-border: rgba(6, 182, 212, 0.35);

  --tag-plumbing-bg: rgba(37, 99, 235, 0.1);
  --tag-plumbing-text: #2563eb;
  --tag-plumbing-border: rgba(37, 99, 235, 0.35);

  --tag-all-bg: rgba(15, 23, 42, 0.06);
  --tag-all-text: #0f172a;
  --tag-all-border: rgba(15, 23, 42, 0.25);

  --pipe-sch40-bg: var(--primary-soft);
  --pipe-sch40-text: var(--primary-dark);
  --pipe-sch40-border: var(--primary);

  --pipe-sch80-bg: var(--tag-plumbing-bg);
  --pipe-sch80-text: var(--tag-plumbing-text);
  --pipe-sch80-border: var(--tag-plumbing-border);
}


*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-size: 16px;
}

body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(15, 118, 110, 0.06), transparent 24rem),
    linear-gradient(180deg, var(--bg-soft) 0%, var(--bg) 100%);
  line-height: 1.6;
}

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

a {
  color: inherit;
  text-decoration: none;
}

.page-wrap {
  width: min(var(--max-width), calc(100% - 2rem));
  margin: 0 auto;
  padding: 2rem 0 4rem;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg-soft) 90%, transparent);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}

.nav {
  width: min(var(--max-width), calc(100% - 2rem));
  margin: 0 auto;
  min-height: 76px;
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 1rem;
}


.brand a {
  font-size: 1.2rem;
  font-weight: 900;
  letter-spacing: 0.02em;
  color: var(--primary);
}

.nav-links {
  display: flex;
  justify-content: center;
  gap: 0.4rem;
  align-items: center;
  flex-wrap: wrap;
}

.nav-actions {
  justify-self: end;
}

.nav-links a {
  color: var(--text-soft);
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.7rem 1rem;
  border-radius: 999px;
  transition: 0.2s ease;
}

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

/* Hero */
.hero {
  padding: 2rem;
  border: 1px solid var(--border-strong);
  background:
    linear-gradient(135deg, var(--primary-soft-2), rgba(240, 249, 255, 0.96)),
    var(--surface);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  margin-bottom: 1.75rem;
}

.hero h1 {
  margin: 0 0 0.8rem;
  font-size: clamp(2rem, 4vw, 3.2rem);
  line-height: 1.05;
  letter-spacing: -0.03em;
}

.hero p {
  margin: 0;
  max-width: 760px;
  color: var(--text-soft);
  font-size: 1.05rem;
}

.home-hero {
  padding: 3.5rem 2rem;
}

.eyebrow {
  display: inline-block;
  margin-bottom: 0.8rem;
  padding: 0.45rem 1rem;
  border-radius: 999px;
  background: var(--primary-soft);
  color: var(--primary-dark);
  font-size: 0.78rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  text-align: center;
  justify-content: center;
  text-align: center;
}

.hero-text {
  margin-top: 1rem !important;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem;
  margin-top: 1.5rem;
}

.btn-link,
.btn-primary,
.btn-secondary {
  appearance: none;
  border: none;
  border-radius: 999px;
  font: inherit;
  font-weight: 700;
  cursor: pointer;
  transition:
    transform 0.15s ease,
    box-shadow 0.15s ease,
    background 0.15s ease,
    border-color 0.15s ease,
    color 0.15s ease;
}

.btn-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0.85rem 1.2rem;
  text-decoration: none;
}

.btn-link-primary,
.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--primary));
  color:#e6fffa;
  box-shadow: 0 15px 24px rgba(13, 148, 136, 0.22);
}

.btn-link-primary:hover,
.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 14px 28px rgba(13, 148, 136, 0.28);
}

.btn-link-secondary,
.btn-secondary {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-soft);
}

.btn-link-secondary:hover,
.btn-secondary:hover {
  background: var(--surface-alt);
  border-color: var(--border-strong);
  transform: translateY(-1px);
}

.home-hero {
  display: flex;
  flex-direction: row;
  align-items: flex-start;
  gap: 2.5rem
}

.hero-left {
  flex: 1.2;
  min-width: 0;
}

.hero-right { 
  flex: 0.8;
  min-width: 0;
}

/* Layout blocks */
.feature-grid,
.content-grid {
  display: grid;
  gap: 1.25rem;
}

.feature-grid {
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

.content-grid {
  grid-template-columns: minmax(0, 1.35fr) minmax(320px, 0.85fr);
  align-items: start;
}

.section-block {
  margin-top: 2rem;
}

.section-heading {
  margin-bottom: 1rem;
}

.section-heading h2,
.card h2,
.card h3 {
  margin-top: 0;
  letter-spacing: -0.02em;
}

.section-heading p {
  margin: 0.4rem 0 0;
  color: var(--text-soft);
}

/* Cards */
.card {
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow-soft);
}

.card p:last-child {
  margin-bottom: 0;
}

.calculator-preview {
  position: relative;
  overflow: hidden;
}

.calculator-preview.coming-soon-card {
  opacity: 0.5;
  cursor: default;
  pointer-events: none;
}

.calculator-preview::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 4px;
  background: linear-gradient(180deg, var(--primary), var(--primary-dark));
  border-radius: 16px 0 0 16px;
  transition: height 0.25s ease;
  height: 40%;
}

.calculator-preview:hover::before {
  height: 100%;
}

.feature-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 12px;
  background: var(--primary-soft);
  font-size: 1.2rem;
  margin-bottom: 0.75rem;
}

.calc-tag {
  display: inline-block;
  margin-bottom: 0.5rem;
  padding: 0.18rem 0.55rem;
  border-radius: 999px;
  font-size: 0.65rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  line-height: 1;
  border: 1px solid;
  box-shadow: var(--shadow-soft);
  backdrop-filter: blur(4px);
}

.calc-tag.load {
  background: var(--tag-load-bg);
  color: var(--tag-load-text);
  border-color: var(--tag-load-border);
}

.calc-tag.ductwork {
  background: var(--tag-duct-bg);
  color: var(--tag-duct-text);
  border-color: var(--tag-duct-border);
}

.calc-tag.airflow {
  background: var(--tag-airflow-bg);
  color: var(--tag-airflow-text);
  border-color: var(--tag-airflow-border);
}

.calc-tag.pressure {
  background: var(--tag-pressure-bg);
  color: var(--tag-pressure-text);
  border-color: var(--tag-pressure-border);
}

.calc-tag.slope {
  background: var(--tag-slope-bg);
  color: var(--tag-slope-text);
  border-color: var(--tag-slope-border);
}

.calc-tag.conversion {
  background: var(--tag-conversion-bg);
  color: var(--tag-conversion-text);
  border-color: var(--tag-conversion-border);
}

.calc-tag.hvac {
  background: var(--tag-hvac-bg);
  color: var(--tag-hvac-text);
  border-color: var(--tag-hvac-border);
}

.calc-tag.plumbing {
  background: var(--tag-plumbing-bg);
  color: var(--tag-plumbing-text);
  border-color: var(--tag-plumbing-border);
}

.calc-tag.all {
  background: var(--tag-all-bg);
  color: var(--tag-all-text);
  border-color: var(--tag-all-border);
}

.pipe-recommendation { 
  margin-top: 12px;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  display: none;
  opacity: 0;
  transform: translateY(4px);
  transition: 0.2s ease;
}

.pipe-recommendation.active {
  display: flex;
  opacity: 1;
  transform: translateY(0);
}

.pipe-card {
  padding: 10px 14px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.9rem;
  border: 1px solid transparent;
  transition: transform  0.15s ease, box-shadow 0.15s ease;
}

.pipe-card:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-soft);
}

.pipe-card.sch40 {
  background: var(--pipe-sch40-bg);
  color: var(--pipe-sch40-text);
  border-color: var(--pipe-sch40-border);
}

.pipe-card.sch80 {
  background: var(--pipe-sch80-bg);
  color: var(--pipe-sch80-text);
  border-color: var(--pipe-sch80-border);
}


/* Forms */
.form-group {
  margin-bottom: 1rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.45rem;
  font-size: 0.94rem;
  font-weight: 700;
  color: var(--text);
}

.form-group input {
  width: 100%;
  min-height: 52px;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: var(--surface-alt);
  color: var(--text);
  font: inherit;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}

.form-group input:focus {
  border-color: rgba(13, 148, 136, 0.5);
  box-shadow: 0 0 0 4px rgba(13, 148, 136, 0.14);
  background: var(--surface);
}

.form-group input::placeholder {
  color: #8ca0b3;
}

.form-group select {
  width: 100%;
  min-height: 52px;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: var(--surface-alt);
  color: var(--text);
  font: inherit;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}

.form-group select:focus {
  border-color: rgba(13, 148, 136, 0.5);
  box-shadow: 0 0 0 4px rgba(13, 148, 136, 0.14);
  background: var(--surface);
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.25rem 0 1rem;
}

.button-row button {
  min-height: 48px;
  padding: 0.8rem 1.15rem;
}

/* Results */
.error-message {
  min-height: 1.5rem;
  margin-bottom: 0.85rem;
  color: var(--error);
  font-size: 0.95rem;
  font-weight: 600;
}

.result-box {
  padding: 1.25rem;
  border-radius: 18px;
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.15), rgba(59, 130, 246,0.15));
  border: 1px solid var(--border);
  box-shadow: var(--border-strong);
}

.result-label {
  margin-bottom: 0.45rem;
  color: var(--text-muted);
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.result-value {
  font-size: clamp(2rem, 3vw, 2.7rem);
  line-height: 1.05;
  font-weight: 800;
  letter-spacing: -0.03em;
  color: var(--primary-dark);
}

.result-subtext {
  margin-top: 0.65rem;
  color: var(--text-soft);
  font-size: 0.98rem;
}

/* Info side */
.info-box {
  padding: 1.25rem;
  border-radius: 18px;
  background: linear-gradient(
    135deg,
    rgba(59, 130, 246, 0.12),
    rgba(16, 185, 129, 0.08)
  );
  border: 1px solid rgba(255, 255, 255, 0.08);
  backdrop-filter: blur(6px);
}

.formula {
  margin: 1rem 0;
  padding: 1rem 1.1rem;
  border: 1px solid rgba(13, 148, 136, 0.2);
  border-radius: 14px;
  background: rgba(204, 251, 241, 0.45);
  color: var(--primary);
  overflow-x: auto;
}

.footer-note {
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.92rem;
}

.site-footer {
  margin: 1rem;
  padding-top: 1rem;
  font-size: 0.82rem;
  display: flex;
  align-content: center;
  justify-content: center;
  
}

.text-link {
  display: inline-block;
  margin-top: 0.9rem;
  color: var(--primary);
  font-weight: 800;
}

.text-link:hover {
  text-decoration: underline;
}

.coming-soon {
  display: inline-block;
  margin-top: 0.9rem;
  padding: 0.42rem 0.75rem;
  background: var(--primary-soft);
  color: var(--primary-dark);
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 800;
}

.formula-card {
  margin: 0 0 1rem;
  font-size: 0.78rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
}

.formula-card .formula {
  color: var(--text);
}

.formula-item {
  margin-bottom: 1rem;
}

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

.formula-label {
  display: block;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.35rem;
}

/* Signup Form */

.email-signup { 
  margin-top: 2.5rem;
  padding: 2.5rem 2rem;
  background: var(--surface-alt);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-soft);
  text-align: center;
}

.signup-heading {
  margin: 0 0 0.4rem;
  font-size: 1.3rem;
  font-weight: 800;
  letter-spacing: -0.02rem;
  color: var(--text);
}

.signup-sub {
  margin: 0 0 1.5rem;
  color: var(--text-soft);
  font-size: 0.95rem;
}

.signup-form {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  flex-wrap: wrap;
}

.signup-form input[type="email"] {
  min-width: 260px;
  min-height: 48px;
  padding: 0.85rem 1rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface-alt);
  color: var(--text);
  font: inherit;
  font-size: 0.95rem;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
  }

  .signup-form input[type="email"]:focus {
    border-color: rgba(13, 148, 136, 0.5);
    box-shadow: 0 0 0 4px rgba(13, 148, 136, 0.14);
  }

  .signup-form input[type="email"]::placeholder {
    color: #8ca0b3;
  }
/*Nav Bar Actions*/
.nav-actions { 
  display:flex;
  align-items: center;
  gap: 0.75rem;
  margin-left: auto;
}

.nav-signin {
  min-height: 38px;
  padding: 0.5rem 1.1rem;
  font-size: 0.88rem;
}
/* =========================
   CARD HOVER EFFECT
========================= */

.calculator-preview {
  transition: 
    transform 0.2s ease,
    box-shadow 0.2s ease,
    border-color 0.2s ease,
    background 0.2s ease;
  cursor: pointer;
  position: relative;
  z-index: 0;
}

.calculator-preview.airflow:hover,
.calculator-preview.ductwork:hover, 
.calculator-preview.pressure:hover, 
.calculator-preview.load:hover, 
.calculator-preview.conversion:hover {
  background: linear-gradient(180deg, var(--primary-soft-2), var(--surface));
  border-color: rgba(13, 148, 136, 0.32);
  box-shadow: 0 14px 30px rgba(15, 118, 110, 0.12);
}

.calculator-preview.plumbing:hover{
  background: linear-gradient(180deg, rgba(37, 99, 235, 0.08), var(--surface));
  border-color: rgba(37, 99, 235, 0.32);
  box-shadow: 0 14px 30px rgba(37, 99, 235, 0.12);
  transform: translateY(-4px);
}

.calculator-preview.airflow::before, 
.calculator-preview.ductwork::before, 
.calculator-preview.pressure::before, 
.calculator-preview.load::before, 
.calculator-preview.conversion::before {
  background: linear-gradient(180deg, var(--primary), var(--primary-dark));
}

.calculator-preview.plumbing::before {
  background: linear-gradient(180deg, #2563eb, #1d4ed8);
}

.calculator-group {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: repeat(3, minmax(0,1fr));
  gap: 1.25rem;
  position: relative;
}
/* =========================
   HAMBURGER MENU
========================= */

.menu-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px;
  height: 44px;
  background: var(--primary-soft-2);
  border: 1px solid var(--border);
  border-radius: 12px;
  cursor: pointer;
  transition: 0.2s ease;
}

.menu-toggle:hover {
  background: var(--surface-alt);
}

.menu-toggle.active {
  background: var(--primary-soft-2);
  border-color: var(--border-strong);
}

/* The 3 lines */
.menu-toggle .bar {
  width: 20px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: 0.3s ease;
  margin: 0 auto;
}

/* Animate into X */
.menu-toggle.active .bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.menu-toggle.active .bar:nth-child(2) {
  opacity: 0;
}

.menu-toggle.active .bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.home-feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.25rem
}

.nav-mobile-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.5rem 1rem;
  margin-top: 0.5rem;
  border-top: 1px solid var(--border);
}

.calc-tag[data-filter].active,
.calc-tag[data-trade].active {
  outline: 2px solid currentColor;
  outline-offset: 2px;
}


/* Responsive */
@media (max-width: 900px) {
  .content-grid {
    grid-template-columns: 1fr;
  }

  .hero,
  .home-hero,
  .card {
    padding: 1.25rem;
  }

  .nav {
    min-height: auto;
    padding: 0.9rem 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
    min-height: auto;
    padding: 0.9rem 0;
    flex-wrap: wrap;
  }

  .nav-links {
    width: 100%;
  }

  .nav-links a {
    text-align: center;
    justify-content: center;
  }

  .calculator-group {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .home-hero {
    flex-direction: column;
  }

  .hero-right {
    width: 100%;
  }

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

  .desktop-only {
    display: none !important;
  }

  .nav-mobile-actions {
    flex-direction: row;
    justify-content: center;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1rem 0.5rem;
  }

  .nav-mobile-actions .nav-signin {
    width: auto;
    min-width: 160px;
    border-radius: 999px;
    min-height: 42px;
    padding: 0.5rem 1.5rem;
    font-size: 0.88rem;
    text-align: center;
  }
  
  .nav-mobile-actions .nav-signin:hover {
    transform: translateY(-1px);
    box-shadow: 0 14px 24px rgba(13, 148, 136, 0.28);
  }
  .nav-mobile-actions .theme-toggle {
    width: 100%;
    border-radius: 12px;
    background: var(--surface-alt);
    border: 1px solid var(--border);
    height: 42px;
    justify-content: center;
  }

  .home-hero { 
    flex-direction: column;
  }

  .hero-right {
    width: 100%;
  }

  .eyebrow {
    white-space: nowrap;
    font-size: 0.7rem;
  }
}

@media (min-width: 901px) {
  .nav-mobile-actions {
    display: none;
  }
}

@media (max-width: 560px) {
  .page-wrap {
    width: min(100% - 1rem, var(--max-width));
    padding-top: 1rem;
  }

  .button-row,
  .hero-actions {
    flex-direction: column;
  }

  .button-row button,
  .btn-link {
    width: 100%;
  }

  .nav-links a {
    padding: 0.6rem 0.8rem;
  }

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

  .home-feature-grid {
    grid-template-columns: 1fr;
  }

  .hero-actions {
    justify-content: center;
  }

  .hero-actions .btn-link {
    min-width: 200px;
    text-align: center;
  }

  .home-hero {
    flex-direction: column !important;
  }

  .hero-right {
    width: 100% !important;
  }

  .eyebrow {
    white-space: normal;
    font-size: 0.68rem;
    letter-spacing: 0.08em;
    text-align: center;
  }
}

@media (min-width: 560px) and (max-width: 900px) {
  .calculator-group {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

/* Mobile behavior */
@media (max-width: 900px) {

  .menu-toggle {
    display: flex;
  }

  .nav {
    flex-wrap: wrap;
  }

  .nav-links {
    display: none;
    width: 100%;
    flex-direction: column;
    align-items: center;
    gap: 0.35rem;
    margin-top: 0.9rem;
    padding: 1,25rem 1rem 1.5rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 16px;
    box-shadow: var(--shadow-soft);
  }

  .nav-links.show {
    display: flex;
  }

  .nav-links a {
    width: auto;
    min-width: 180px;
    text-align: center;
    padding: 0.85rem 1rem;
    border-radius: 12px;
  }

  .nav-mobile-actions {
    width: 100%;
    display:flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
    margin-top: 0.75rem;
    padding-top: 0.9rem;
    border-top: 1px solid var(--border);
  }
}

.menu-toggle.active .bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.menu-toggle.active .bar:nth-child(2) {
  opacity: 0;
}

.menu-toggle.active .bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Dark mode colors */
[data-theme="dark"] {
  --bg: #0b1326;
  --bg-soft: #131b2e;
  --surface: #171f33;
  --surface-alt: #222a3d;

  --border: rgba(61, 73, 71, 0.2);
  --border-strong: rgba(61, 73, 71, 0.4);

  --text: #e8edf5;
  --text-soft: #8b97b0;
  --text-muted: #5a6480;

  --primary: #3cddc7;
  --primary-dark: #00a392;
  --primary-soft: #0d2e2b;
  --primary-soft-2: #0a1f1e;

  --secondary: #e2e8f0;
  --secondary-soft: #cbd5e1;

  --shadow: 0 12px 40px rgba(0, 0, 0, 0.5);
  --shadow-soft: 0 6px 24px rgba(0, 0, 0, 0.35);

  /* Tag Colors for Dark Theme*/

  --tag-airflow-bg: rgba(60, 221, 199, 0.12);
  --tag-airflow-text: var(--primary);
  --tag-airflow-border: rgba(60, 221, 199, 0.35);

  --tag-duct-bg: rgba(203, 213, 225, 0.06);
  --tag-duct-text: var(--secondary);
  --tag-duct-border: rgba(203, 213, 225, 0.18);

  --tag-load-bg: rgba(249, 115, 22, 0.12);
  --tag-load-text: #ffb37a;
  --tag-load-border: rgba(249, 115, 22, 0.35);

  --tag-pressure-bg: rgba(124, 58, 237, 0.1);
  --tag-pressure-text: #7c3aed;
  --tag-pressure-border: rgba(124, 58, 237, 0.3);

  --tag-slope-bg: rgba(163, 230, 53, 0.1);
  --tag-slope-text: #a3e635;
  --tag-slope-border: rgba(163, 230, 52, 0.3);

  --tag-conversion-bg: rgba(100, 116, 139, 0.1);
  --tag-conversion-text: #64748b;
  --tag-conversion-border: rgba(100, 116, 139, 0.3);

  --tag-all-bg: rgba(225, 225, 225, 0.06);
  --tag-all-text: #e8edf5;
  --tag-all-border: rgba(255, 255, 255, 0.2);

  --tag-hvac-bg: rgba(6, 182, 212, 0.12);
  --tag-hvac-text: #22d3ee;
  --tag-hvac-border: rgba(6, 182, 212, 0.35);

  --tag-plumbing-bg: rgba(96, 165, 250, 0.1);
  --tag-plumbing-text: #60a5fa;
  --tag-plumbing-border: rgba(96, 165, 250, 0.3);
}

/* System preference default */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0b1326;
    --bg-soft: #131b2e;
    --surface: #171f33;
    --surface-alt: #222a3d;

    --border: rgba(61, 73, 71, 0.2);
    --border-strong: rgba(61, 73, 71, 0.4);

    --text: #e8edf5;
    --text-soft: #8b97b0;
    --text-muted: #5a6480;

    --primary: #3cddc7;
    --primary-dark: #00a392;
    --primary-soft: #0d2e2b;
    --primary-soft-2: #0a1f1e;

    --secondary: #e2e8f0;
    --secondary-soft: #cbd5e1;

    --shadow: 0 12px 40px rgba(0, 0, 0, 0.5);
    --shadow-soft: 0 6px 24px rgba(0, 0, 0, 0.35);

    --tag-all-bg: rgba(225, 225, 225, 0.06);
    --tag-all-text: #e8edf5;
    --tag-all-border: rgba(255, 255, 255, 0.2);

    --tag-hvac-bg: rgba(6, 182, 212, 0.12);
    --tag-hvac-text: #22d3ee;
    --tag-hvac-border: rgba(6, 182, 212, 0.35);

    --tag-plumbing-bg: rgba(96, 165, 250, 0.1);
    --tag-plumbing-text: #60a5fa;
    --tag-plumbing-border: rgba(96, 165, 250, 0.3);

    --tag-airflow-bg: rgba(60, 221, 199, 0.12);
    --tag-airflow-text: var(--primary);
    --tag-airflow-border: rgba(60, 221, 199, 0.35);

    --tag-load-bg: rgba(249, 115, 22, 0.12);
    --tag-load-text: #ffb37a;
    --tag-load-border: rgba(249, 115, 22, 0.35);

    --tag-duct-bg: rgba(203, 213, 225, 0.06);
    --tag-duct-text: var(--secondary);
    --tag-duct-border: rgba(203, 213, 225, 0.18);

    --tag-slope-bg: rgba(163, 230, 53, 0.1);
    --tag-slope-text: #a3e635;
    --tag-slope-border: rgba(163, 230, 52, 0.3);
  }
}

/* Manual dark mode */
[data-theme="dark"] body {
  background:
  radial-gradient(circle at top left, rgba(20, 184, 166, 0.07), transparent 24rem),
  linear-gradient(180deg, var(--bg-soft) 0%, var(--bg) 100%);
}

/* System preference dark mode */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) body {
    background: 
    radial-gradient(circle at top left, rgba(20, 184, 166, 0.07), transparent 24rem),
    linear-gradient(180deg, var(--bg-soft) 0%, var(--bg) 100%);
  }
}

/* Theme toggle button */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text-soft);
  cursor: pointer;
  font-size: 1rem;
  transition: background 0.2s ease, border-color 0.2s ease, color 0.2s ease;
  flex-shrink: 0;
}

.theme-toggle:hover {
  background: var(--surface-alt);
  border-color: var(--border-strong);
  color: var(--text);
}

.nav-links .theme-toggle {
  background: transparent;
  border: none;
  box-shadow: none;
  padding: 0.7rem 1rem;
  width: auto;
  height: auto;
  font-size: 1rem;
  border-radius: 999px;
}

.nav-links .theme-toggle:hover {
  background: var(--primary-soft-2);
  border: none;
}


[data-theme="dark"] body {
  background:
    radial-gradient(circle at top left, rgba(60, 221, 199, 0.05), transparent 24rem),
    linear-gradient(180deg, var(--bg-soft) 0%, var(--bg) 100%);
}

[data-theme="dark"] .calculator-preview.airflow:hover,
[data-theme="dark"] .calculator-preview.ductwork:hover,
[data-theme="dark"] .calculator-preview.pressure:hover,
[data-theme="dark"] .calculator-preview.load:hover,
[data-theme="dark"] .calculator-preview.conversion:hover {
  background: linear-gradient(180deg, var(--primary-soft-2), var(--surface));
  border-color: rgba(60, 221, 199, 0.15);
  box-shadow: 0 14px 40px rgba(0, 0, 0, 0.4);
}

[data-theme="dark"] .calculator-preview.plumbing:hover {
  background: linear-gradient(180deg, rgba(37, 99, 235, 0.06), var(--surface));
  border-color: rgba(37, 99, 235, 0.2);
  box-shadow: 0 14px 40px rgba(0, 0, 0, 0.4);
}

[data-theme="dark"] .nav-signin {
  background: linear-gradient(135deg, var(--primary-dark), var(--primary));
  color: #0a1f1e;
  box-shadow: 0 10px 24px  rgba(13, 148, 136, 0.15);
}

[data-theme="dark"] .form-group input, 
[data-theme="dark"] .form-group select {
  background: #2a3450;
  border-color: rgba(255, 255, 255, 0.15);
  color: var(--text);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) body {
    background:
      radial-gradient(circle at top left, rgba(60, 221, 199, 0.05), transparent 24rem),
      linear-gradient(180deg, var(--bg-soft) 0%, var(--bg) 100%);
  }

  :root:not([data-them="light"]) .nav-signin {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
    color: #0a1f1e;
    box-shadow: 0 10px 25px rgba(13, 148, 136, 0.15);
  }

  :root:not([data-theme="light"]) .form-group input,
  :root:not([data-theme="light"]) .form-group select {
    background: #2a3450;
    border-color: rgba(255, 255, 255, 0.15);
    color: var(--text);
  }
}


[data-theme="dark"] .hero,
[data-theme="dark"] .home-hero {
  background: var(--surface);
  border-color: var(--border);
  box-shadow: var(--shadow);
}

[data-theme="dark"] .btn-link-primary,
[data-theme="dark"] .btn-primary {
  background: linear-gradient(135deg, var(--primary-dark), var(--primary));
  box-shadow: 0 10px 24px rgba(13, 148, 136, 0.15);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .hero,
  :root:not([data-theme="light"]) .home-hero {
    background: var(--surface);
    border-color: var(--border);
  }

  :root:not([data-theme="light"]) .btn-link-primary,
  :root:not([data-theme="light"]) .btn-primary {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
    box-shadow: 0 10px 24px rgba(13, 148, 136, 0.15);
  }
}