/* ============================================================
   ALTITUDE PERFORMANCE LAB — Design System & Styles
   ============================================================ */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap');

/* --- CSS Variables --- */
:root {
  --bg-primary:    #0D1117;
  --bg-secondary:  #161B22;
  --bg-tertiary:   #21262D;
  --border:        #30363D;
  --border-subtle: #21262D;
  --text-primary:  #E6EDF3;
  --text-secondary:#A8B3BD;
  --text-muted:    #768390;
  --accent:        #00B4D8;
  --accent-dark:   #0096B4;
  --accent-dim:    rgba(0, 180, 216, 0.12);
  --accent-glow:   rgba(0, 180, 216, 0.25);
  --success:       #3FB950;
  --success-dim:   rgba(63, 185, 80, 0.12);
  --warning:       #F0A741;
  --warning-dim:   rgba(240, 167, 65, 0.12);
  --danger:        #F85149;
  --danger-dim:    rgba(248, 81, 73, 0.12);
  --font-sans:     'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono:     'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
  --radius-sm:     4px;
  --radius:        8px;
  --radius-lg:     12px;
  --radius-xl:     16px;
  --transition:    0.2s ease;
  --shadow-sm:     0 1px 4px rgba(0, 0, 0, 0.3);
  --shadow:        0 4px 24px rgba(0, 0, 0, 0.4);
  --shadow-lg:     0 8px 48px rgba(0, 0, 0, 0.5);
  --max-width:     1200px;
  --nav-height:    64px;
}

/* ============================================================
   RESET & BASE
   ============================================================ */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img { max-width: 100%; display: block; }
a { color: var(--accent); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--accent-dark); }

/* ============================================================
   TYPOGRAPHY
   ============================================================ */

h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

h1 { font-size: clamp(2rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2.25rem); }
h3 { font-size: clamp(1.125rem, 2vw, 1.5rem); }
h4 { font-size: 1.125rem; }

p { color: var(--text-secondary); line-height: 1.7; }

.label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
}

.mono { font-family: var(--font-mono); }

/* ============================================================
   LAYOUT
   ============================================================ */

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 96px 0;
}

.section--sm {
  padding: 64px 0;
}

.section-header {
  margin-bottom: 56px;
}

.section-header .label {
  display: inline-block;
  margin-bottom: 12px;
}

.section-header h2 {
  margin-bottom: 16px;
}

.section-header p {
  max-width: 560px;
  font-size: 1.0625rem;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
}

/* ============================================================
   NAVIGATION
   ============================================================ */

.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: rgba(13, 17, 23, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  display: flex;
  align-items: center;
}

.nav__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav__logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
}

.nav__logo-mark {
  width: 32px;
  height: 32px;
  background: var(--accent-dim);
  border: 1px solid var(--accent);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--accent);
  flex-shrink: 0;
}

.nav__logo-text {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

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

.nav__links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav__links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition);
}

.nav__links a:hover,
.nav__links a.active {
  color: var(--text-primary);
}

.nav__cta {
  display: flex;
  align-items: center;
  gap: 16px;
}

/* Hamburger */
.nav__hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav__hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-secondary);
  border-radius: 2px;
  transition: all var(--transition);
}

/* Mobile nav */
.nav__mobile {
  display: none;
  position: fixed;
  top: var(--nav-height);
  left: 0;
  right: 0;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  padding: 24px;
  z-index: 99;
  flex-direction: column;
  gap: 16px;
}

.nav__mobile.open { display: flex; }

.nav__mobile a {
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 8px 0;
  border-bottom: 1px solid var(--border-subtle);
}

.nav__mobile a:last-child { border-bottom: none; }

/* ============================================================
   BUTTONS
   ============================================================ */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: var(--radius);
  font-family: var(--font-sans);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  border: 1px solid transparent;
  text-decoration: none;
  white-space: nowrap;
}

.btn--primary {
  background: var(--accent);
  color: #0D1117;
  border-color: var(--accent);
}

.btn--primary:hover {
  background: var(--accent-dark);
  border-color: var(--accent-dark);
  color: #0D1117;
  transform: translateY(-1px);
  box-shadow: 0 4px 16px var(--accent-glow);
}

.btn--outline {
  background: transparent;
  color: var(--accent);
  border-color: var(--accent);
}

.btn--outline:hover {
  background: var(--accent-dim);
  color: var(--accent);
  transform: translateY(-1px);
}

.btn--ghost {
  background: transparent;
  color: var(--text-secondary);
  border-color: var(--border);
}

.btn--ghost:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.btn--lg {
  padding: 14px 28px;
  font-size: 1rem;
  border-radius: var(--radius-lg);
}

.btn--sm {
  padding: 6px 14px;
  font-size: 0.8125rem;
}

/* ============================================================
   BADGES
   ============================================================ */

.badge {
  display: inline-flex;
  align-items: center;
  padding: 3px 10px;
  border-radius: 100px;
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.02em;
}

.badge--accent   { background: var(--accent-dim);   color: var(--accent);   border: 1px solid rgba(0,180,216,0.3); }
.badge--success  { background: var(--success-dim);  color: var(--success);  border: 1px solid rgba(63,185,80,0.3); }
.badge--warning  { background: var(--warning-dim);  color: var(--warning);  border: 1px solid rgba(240,167,65,0.3); }
.badge--danger   { background: var(--danger-dim);   color: var(--danger);   border: 1px solid rgba(248,81,73,0.3); }
.badge--muted    { background: var(--bg-tertiary);  color: var(--text-secondary); border: 1px solid var(--border); }

/* ============================================================
   CARDS
   ============================================================ */

.card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.card:hover {
  border-color: rgba(0, 180, 216, 0.4);
  box-shadow: var(--shadow);
}

.card--flush { padding: 0; overflow: hidden; }

.card__icon {
  width: 44px;
  height: 44px;
  background: var(--accent-dim);
  border: 1px solid rgba(0,180,216,0.25);
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  font-size: 1.25rem;
}

.card h3 {
  font-size: 1.0625rem;
  margin-bottom: 10px;
}

.card p {
  font-size: 0.9rem;
  line-height: 1.65;
}

/* ============================================================
   FORMS
   ============================================================ */

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-label {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-secondary);
  letter-spacing: 0.01em;
}

.form-input,
.form-select {
  width: 100%;
  padding: 10px 14px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  transition: border-color var(--transition), box-shadow var(--transition);
  appearance: none;
  -webkit-appearance: none;
}

.form-input:focus,
.form-select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-dim);
}

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

.form-select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%238B949E' stroke-width='1.5' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 14px center;
  padding-right: 40px;
  cursor: pointer;
}

.form-select option {
  background: var(--bg-secondary);
}

.input-group {
  display: flex;
  align-items: stretch;
}

.input-group .form-input {
  border-radius: var(--radius) 0 0 var(--radius);
  border-right: none;
  flex: 1;
}

.input-group .btn {
  border-radius: 0 var(--radius) var(--radius) 0;
  flex-shrink: 0;
}

.input-with-unit {
  position: relative;
}

.input-with-unit .form-input {
  padding-right: 52px;
}

.input-unit {
  position: absolute;
  right: 14px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-muted);
  pointer-events: none;
  font-family: var(--font-mono);
}

/* Unit toggle */
.unit-toggle {
  display: flex;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.unit-toggle button {
  flex: 1;
  padding: 6px 12px;
  background: none;
  border: none;
  color: var(--text-secondary);
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
  font-family: var(--font-mono);
}

.unit-toggle button.active {
  background: var(--accent);
  color: #0D1117;
}

/* ============================================================
   HERO
   ============================================================ */

.hero {
  padding-top: calc(var(--nav-height) + 80px);
  padding-bottom: 96px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background:
    radial-gradient(ellipse 60% 50% at 70% 40%, rgba(0, 180, 216, 0.06) 0%, transparent 70%),
    radial-gradient(ellipse 40% 60% at 20% 70%, rgba(0, 100, 150, 0.04) 0%, transparent 70%);
  pointer-events: none;
}

/* Subtle dot grid */
.hero::after {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background-image: radial-gradient(circle, var(--border) 1px, transparent 1px);
  background-size: 32px 32px;
  opacity: 0.4;
  pointer-events: none;
}

.hero__inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 64px;
  align-items: center;
  position: relative;
  z-index: 1;
}

.hero__content { max-width: 560px; }

.hero__eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 24px;
}

.hero__eyebrow-dot {
  width: 6px;
  height: 6px;
  background: var(--success);
  border-radius: 50%;
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; box-shadow: 0 0 0 0 rgba(63,185,80,0.4); }
  50% { opacity: 0.8; box-shadow: 0 0 0 6px rgba(63,185,80,0); }
}

.hero__eyebrow span {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-secondary);
  letter-spacing: 0.08em;
}

.hero h1 {
  margin-bottom: 20px;
  color: var(--text-primary);
}

.hero h1 span { color: var(--accent); }

.hero__sub {
  font-size: 1.0625rem;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 40px;
  max-width: 480px;
}

.hero__actions {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.hero__email-form {
  display: flex;
  gap: 0;
  max-width: 460px;
}

.hero__email-form .form-input {
  border-radius: var(--radius) 0 0 var(--radius);
  border-right: none;
  background: var(--bg-secondary);
}

.hero__email-form .btn {
  border-radius: 0 var(--radius) var(--radius) 0;
}

.hero__cta-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.hero__cta-link:hover { color: var(--accent); }

.hero__cta-link svg { transition: transform var(--transition); }
.hero__cta-link:hover svg { transform: translateX(3px); }

/* Hero visual — data readout card */
.hero__visual {
  display: flex;
  justify-content: center;
  align-items: center;
}

/* ── CALCULATOR OUTPUT PREVIEW (hero visual) ───────────── */
.calc-preview {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  width: 100%;
  max-width: 420px;
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.calc-preview__header {
  padding: 13px 18px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg-tertiary);
}

.calc-preview__label {
  font-size: 0.65rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  color: var(--accent);
  text-transform: uppercase;
}

.calc-preview__meta {
  font-size: 0.72rem;
  color: var(--text-muted);
}

.calc-preview__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1px;
  background: var(--border);
}

.calc-preview__card {
  background: var(--bg-secondary);
  padding: 14px 14px 12px;
  display: flex;
  flex-direction: column;
}

.calc-preview__card:nth-child(5) {
  grid-column: 1 / -1;
  border-top: 1px solid var(--border);
}

.calc-preview__card-label {
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.calc-preview__card-value {
  font-size: 1.5rem;
  font-weight: 800;
  line-height: 1;
  margin-bottom: 4px;
}

.calc-preview__card-sub {
  font-size: 0.68rem;
  color: var(--text-muted);
  margin-bottom: 7px;
}

.calc-preview__card-hint {
  font-size: 0.68rem;
  color: var(--text-muted);
  font-style: italic;
  line-height: 1.4;
  padding-top: 6px;
  border-top: 1px solid var(--border);
  margin-top: auto;
}

.calc-preview__badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 12px;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.calc-preview__badge--moderate {
  background: rgba(210,153,34,0.15);
  color: var(--warning);
  border: 1px solid rgba(210,153,34,0.3);
}

/* Locked teaser section */
.calc-preview__gate {
  border-top: 1px solid var(--border);
  padding: 14px 16px;
  position: relative;
  background: var(--bg-secondary);
}

.calc-preview__gate-blur {
  display: flex;
  flex-direction: column;
  gap: 7px;
  margin-bottom: 10px;
  opacity: 0.35;
  filter: blur(3px);
  pointer-events: none;
}

.calc-preview__gate-row {
  height: 10px;
  width: 100%;
  background: var(--border);
  border-radius: 4px;
}

.calc-preview__gate-label {
  font-size: 0.72rem;
  color: var(--text-muted);
  text-align: center;
  font-style: italic;
}

/* ============================================================
   HOW IT WORKS
   ============================================================ */

.how-it-works { background: var(--bg-secondary); }

.steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0;
  position: relative;
}

.steps::before {
  content: '';
  position: absolute;
  top: 22px;
  left: calc(33.33% - 0px);
  right: calc(33.33%);
  height: 1px;
  background: var(--border);
}

.step {
  padding: 0 32px;
  text-align: left;
}

.step:first-child { padding-left: 0; }
.step:last-child  { padding-right: 0; }

.step__number {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--bg-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--accent);
  margin-bottom: 24px;
  position: relative;
  z-index: 1;
}

.step h3 { font-size: 1rem; margin-bottom: 10px; }
.step p  { font-size: 0.875rem; }

/* ============================================================
   TOOL & ARTICLE CARDS
   ============================================================ */

.tool-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}

.tool-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s ease;
}

.tool-card:hover { border-color: rgba(0,180,216,0.4); box-shadow: var(--shadow); }
.tool-card:hover::before { transform: scaleX(1); }

.tool-card__icon {
  width: 48px; height: 48px;
  background: var(--accent-dim);
  border: 1px solid rgba(0,180,216,0.2);
  border-radius: var(--radius);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.375rem;
  margin-bottom: 20px;
}

.tool-card h3 { font-size: 1.0625rem; margin-bottom: 10px; }
.tool-card p  { font-size: 0.875rem; flex: 1; margin-bottom: 24px; }

.tool-card__footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: auto;
}

.article-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
}

.article-card:hover { border-color: rgba(0,180,216,0.4); transform: translateY(-2px); box-shadow: var(--shadow); }

.article-card__body { padding: 24px; flex: 1; display: flex; flex-direction: column; }
.article-card__category {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.article-card h3 { font-size: 1rem; margin-bottom: 10px; line-height: 1.4; }
.article-card p  { font-size: 0.875rem; flex: 1; margin-bottom: 20px; }
.article-card__meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-top: auto;
  padding-top: 16px;
  border-top: 1px solid var(--border-subtle);
}

.article-card__read-time {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

/* ============================================================
   EMAIL CAPTURE SECTION
   ============================================================ */

.email-capture {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, rgba(0, 180, 216, 0.05) 100%);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 64px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.email-capture::before {
  content: '';
  position: absolute;
  top: -50%; left: -50%;
  width: 200%; height: 200%;
  background: radial-gradient(ellipse at center, rgba(0,180,216,0.06) 0%, transparent 60%);
  pointer-events: none;
}

.email-capture__inner { position: relative; z-index: 1; max-width: 560px; margin: 0 auto; }
.email-capture__label { margin-bottom: 16px; }
.email-capture h2 { margin-bottom: 16px; }
.email-capture p  { margin-bottom: 32px; font-size: 1.0625rem; }

.email-capture__form {
  display: flex;
  gap: 0;
  max-width: 420px;
  margin: 0 auto 16px;
}

.email-capture__form .form-input {
  border-radius: var(--radius) 0 0 var(--radius);
  border-right: none;
}

.email-capture__form .btn {
  border-radius: 0 var(--radius) var(--radius) 0;
  white-space: nowrap;
}

.email-capture__disclaimer {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ============================================================
   CALCULATOR
   ============================================================ */

.calculator-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  align-items: start;
}

.hub-layout {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 48px;
  align-items: start;
}

.calculator-form {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  overflow: hidden;
}

.calculator-form__header {
  padding: 24px 28px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.calculator-form__header-left { display: flex; align-items: center; gap: 12px; }

.calculator-form__icon {
  width: 40px; height: 40px;
  background: var(--accent-dim);
  border: 1px solid rgba(0,180,216,0.2);
  border-radius: var(--radius);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.125rem;
}

.calculator-form__title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 2px;
}

.calculator-form__subtitle {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.calculator-form__body {
  padding: 28px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.calculator-form__row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 12px;
  align-items: end;
}

.calculator-form__footer {
  padding: 20px 28px;
  border-top: 1px solid var(--border);
}

/* Results Panel */
.results-panel {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.results-placeholder {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 48px 28px;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}

.results-placeholder__icon {
  font-size: 2.5rem;
  opacity: 0.4;
}

.results-placeholder h3 { font-size: 1.0625rem; color: var(--text-secondary); font-weight: 500; }
.results-placeholder p  { font-size: 0.875rem; max-width: 260px; }

.result-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  transition: border-color var(--transition);
}

.result-card--accent  { border-color: rgba(0,180,216,0.3);  background: linear-gradient(135deg, var(--bg-secondary), rgba(0,180,216,0.04)); }
.result-card--danger  { border-color: rgba(248,81,73,0.3);   background: linear-gradient(135deg, var(--bg-secondary), rgba(248,81,73,0.04)); }
.result-card--warning { border-color: rgba(240,167,65,0.3);  background: linear-gradient(135deg, var(--bg-secondary), rgba(240,167,65,0.04)); }
.result-card--success { border-color: rgba(63,185,80,0.3);   background: linear-gradient(135deg, var(--bg-secondary), rgba(63,185,80,0.04)); }

.result-card__header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: 16px;
}

.result-card__label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.result-card__value {
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: 500;
  line-height: 1;
}

.result-card__value.accent  { color: var(--accent); }
.result-card__value.danger  { color: var(--danger); }
.result-card__value.warning { color: var(--warning); }
.result-card__value.success { color: var(--success); }

.result-card__description {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.result-card__bar {
  height: 6px;
  background: var(--bg-tertiary);
  border-radius: 3px;
  margin-top: 14px;
  overflow: hidden;
}

.result-card__bar-fill {
  height: 100%;
  border-radius: 3px;
  transition: width 1s ease;
}

/* Report gate */
.report-gate {
  background: linear-gradient(135deg, var(--bg-secondary), rgba(0,180,216,0.05));
  border: 1px solid rgba(0,180,216,0.25);
  border-radius: var(--radius-xl);
  padding: 32px;
  display: none;
}

.report-gate.visible { display: block; }

.report-gate__header { margin-bottom: 20px; }
.report-gate h3 { font-size: 1.125rem; margin-bottom: 8px; }
.report-gate p  { font-size: 0.875rem; }

.report-gate__features {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 24px;
}

.report-gate__feature {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.report-gate__feature::before {
  content: '✓';
  width: 18px;
  height: 18px;
  background: var(--success-dim);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.7rem;
  color: var(--success);
  flex-shrink: 0;
}

.report-gate__form { display: flex; gap: 0; }
.report-gate__form .form-input {
  border-radius: var(--radius) 0 0 var(--radius);
  border-right: none;
}
.report-gate__form .btn {
  border-radius: 0 var(--radius) var(--radius) 0;
  white-space: nowrap;
}

.report-gate__success {
  display: none;
  text-align: center;
  padding: 20px;
}

.report-gate__success-icon { font-size: 2rem; margin-bottom: 12px; }
.report-gate__success h4 { margin-bottom: 8px; }

/* ============================================================
   RESOURCES PAGE
   ============================================================ */

.resources-filters {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 40px;
}

.filter-btn {
  padding: 7px 16px;
  border-radius: 100px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
  font-family: var(--font-sans);
}

.filter-btn:hover { border-color: var(--accent); color: var(--accent); }
.filter-btn.active { background: var(--accent); border-color: var(--accent); color: #0D1117; }

.articles-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.article-card[data-hidden="true"] { display: none; }

/* ============================================================
   ALTITUDE ZONE INDICATOR
   ============================================================ */

.altitude-zones {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
}

.altitude-zones__title {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 16px;
}

.altitude-zone {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 0;
  border-bottom: 1px solid var(--border-subtle);
}

.altitude-zone:last-child { border-bottom: none; }

.altitude-zone__dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}

.altitude-zone__label { font-size: 0.8rem; color: var(--text-secondary); flex: 1; }
.altitude-zone__range { font-family: var(--font-mono); font-size: 0.75rem; color: var(--text-muted); }

/* ============================================================
   FOOTER
   ============================================================ */

.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  padding: 56px 0 32px;
}

.footer__inner {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer__brand { max-width: 300px; }
.footer__logo {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
  text-decoration: none;
}

.footer__logo-mark {
  width: 28px; height: 28px;
  background: var(--accent-dim);
  border: 1px solid var(--accent);
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  font-weight: 500;
  color: var(--accent);
}

.footer__logo-text {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-primary);
}

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

.footer__brand p {
  font-size: 0.875rem;
  margin-bottom: 20px;
  line-height: 1.65;
}

.footer__powered {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.8rem;
  color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 5px 10px;
  text-decoration: none;
  transition: all var(--transition);
}

.footer__powered:hover { border-color: var(--accent); color: var(--accent); }
.footer__powered-label { opacity: 0.6; }

.footer__col-title {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  letter-spacing: 0.01em;
}

.footer__links {
  display: flex;
  flex-direction: column;
  gap: 10px;
  list-style: none;
}

.footer__links a {
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition);
}

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

.footer__bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 24px;
  border-top: 1px solid var(--border-subtle);
}

.footer__copyright {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ============================================================
   PAGE HERO (inner pages)
   ============================================================ */

.page-hero {
  padding-top: calc(var(--nav-height) + 64px);
  padding-bottom: 64px;
  position: relative;
  overflow: hidden;
}

.page-hero::after {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background-image: radial-gradient(circle, var(--border) 1px, transparent 1px);
  background-size: 32px 32px;
  opacity: 0.3;
  pointer-events: none;
}

.page-hero__inner {
  position: relative;
  z-index: 1;
  max-width: 680px;
}

/* ============================================================
   UTILITY CLASSES
   ============================================================ */

.text-accent   { color: var(--accent); }
.text-muted    { color: var(--text-muted); }
.text-secondary{ color: var(--text-secondary); }
.text-center   { text-align: center; }
.text-danger   { color: var(--danger); }
.text-success  { color: var(--success); }
.text-warning  { color: var(--warning); }

.mt-0  { margin-top: 0; }
.mt-4  { margin-top: 4px; }
.mt-8  { margin-top: 8px; }
.mt-12 { margin-top: 12px; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mt-48 { margin-top: 48px; }

.mb-8  { margin-bottom: 8px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.mb-32 { margin-bottom: 32px; }

.hidden { display: none !important; }

.divider {
  height: 1px;
  background: var(--border);
  margin: 40px 0;
}

/* Success message */
.success-msg {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 12px 16px;
  background: var(--success-dim);
  border: 1px solid rgba(63,185,80,0.3);
  border-radius: var(--radius);
  font-size: 0.875rem;
  color: var(--success);
}

.success-msg.visible { display: flex; }

/* ============================================================
   ANIMATIONS
   ============================================================ */

@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

.animate-in {
  animation: fadeInUp 0.4s ease forwards;
}

/* ============================================================
   RESPONSIVE
   ============================================================ */

@media (max-width: 1024px) {
  .hero__inner {
    grid-template-columns: 1fr;
    gap: 48px;
  }

  .hero__content { max-width: 100%; }
  .hero__visual { justify-content: flex-start; }
  .data-readout { max-width: 100%; }

  .grid-3 { grid-template-columns: repeat(2, 1fr); }

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

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

@media (max-width: 768px) {
  .section { padding: 64px 0; }

  .nav__links { display: none; }
  .nav__cta .btn { display: none; }
  .nav__hamburger { display: flex; }

  .hero { padding-top: calc(var(--nav-height) + 48px); padding-bottom: 64px; }

  h1 { font-size: 2rem; }

  .hero__email-form { flex-direction: column; }
  .hero__email-form .form-input { border-radius: var(--radius); border-right: 1px solid var(--border); }
  .hero__email-form .btn { border-radius: var(--radius); }

  .steps { grid-template-columns: 1fr; gap: 32px; }
  .steps::before { display: none; }
  .step { padding: 0; }

  .grid-3 { grid-template-columns: 1fr; }
  .grid-2 { grid-template-columns: 1fr; }

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

  .email-capture { padding: 40px 24px; }
  .email-capture__form { flex-direction: column; }
  .email-capture__form .form-input { border-radius: var(--radius); border-right: 1px solid var(--border); }
  .email-capture__form .btn { border-radius: var(--radius); }

  .footer__inner { grid-template-columns: 1fr; gap: 32px; }
  .footer__bottom { flex-direction: column; gap: 12px; text-align: center; }

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

  .report-gate__form { flex-direction: column; }
  .report-gate__form .form-input { border-radius: var(--radius); border-right: 1px solid var(--border); }
  .report-gate__form .btn { border-radius: var(--radius); }

  .resources-filters { gap: 6px; }
}

@media (max-width: 480px) {
  .container { padding: 0 16px; }
  h1 { font-size: 1.75rem; }
  .btn--lg { padding: 12px 20px; font-size: 0.9375rem; }
  .articles-grid { grid-template-columns: 1fr; }
}


/* ============================================================
   TOPIC NAV (hub switcher on topic pages)
   ============================================================ */

.topic-nav {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.topic-nav__item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 7px 16px;
  border-radius: var(--radius);
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  transition: all var(--transition);
}

.topic-nav__item:hover {
  border-color: rgba(0, 180, 216, 0.4);
  color: var(--accent);
  background: var(--accent-dim);
}

.topic-nav__item.active {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-dim);
}


/* ============================================================
   TOPIC HUB CARDS (home page)
   ============================================================ */

.topic-hub-card {
  display: flex;
  flex-direction: column;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  text-decoration: none;
  transition: border-color var(--transition), box-shadow var(--transition), transform var(--transition);
  cursor: pointer;
}

.topic-hub-card:hover {
  border-color: rgba(0, 180, 216, 0.5);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  transform: translateY(-2px);
}

.topic-hub-card__icon {
  font-size: 2rem;
  margin-bottom: 16px;
  line-height: 1;
}

.topic-hub-card__label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

.topic-hub-card h3 {
  font-size: 1.125rem;
  margin-bottom: 10px;
  color: var(--text-primary);
}

.topic-hub-card p {
  font-size: 0.9rem;
  line-height: 1.65;
  color: var(--text-secondary);
  flex: 1;
  margin-bottom: 20px;
}

.topic-hub-card__tools {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 20px;
}

.topic-hub-card__cta {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent);
  margin-top: auto;
}

.topic-hub-card:hover .topic-hub-card__cta svg {
  transform: translateX(3px);
}

.topic-hub-card__cta svg {
  transition: transform var(--transition);
}


/* ============================================================
   ACCLIMATIZATION TIMELINE (results panel)
   ============================================================ */

.acclim-timeline {
  display: flex;
  flex-direction: column;
}

.acclim-phase {
  display: flex;
  gap: 12px;
  padding: 12px 0;
  border-bottom: 1px solid var(--border-subtle);
}

.acclim-phase:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.acclim-phase__dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  margin-top: 6px;
  flex-shrink: 0;
}

.acclim-phase__day {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--text-muted);
  width: 72px;
  flex-shrink: 0;
  margin-top: 3px;
  line-height: 1.4;
}

.acclim-phase__content {
  flex: 1;
}

.acclim-phase__title {
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--text-primary);
  margin-bottom: 3px;
}

.acclim-phase__desc {
  font-size: 0.8rem;
  color: var(--text-muted);
  line-height: 1.5;
}


/* ============================================================
   ZONE TABLE (training zones calculator)
   ============================================================ */

.zone-table {
  width: 100%;
  border-collapse: collapse;
}

.zone-table th {
  text-align: left;
  padding: 7px 10px;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  border-bottom: 1px solid var(--border);
}

.zone-table td {
  padding: 9px 10px;
  border-bottom: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 0.78rem;
}

.zone-table tr:last-child td {
  border-bottom: none;
}

.zone-table td:first-child {
  color: var(--text-primary);
  font-weight: 500;
}

.zone-table td:last-child {
  color: var(--accent);
}


/* ============================================================
   METRIC TOGGLE BUTTON (training page)
   ============================================================ */

.metric-toggle-btn.active {
  background: var(--accent-dim) !important;
  border-color: var(--accent) !important;
  color: var(--accent) !important;
}


/* ============================================================
   RESPONSIVE — new components
   ============================================================ */

@media (max-width: 768px) {
  .topic-hub-card {
    padding: 20px;
  }

  .acclim-phase__day {
    width: 56px;
    font-size: 0.68rem;
  }

  .zone-table th,
  .zone-table td {
    padding: 7px 6px;
    font-size: 0.72rem;
  }

  .zone-table th:nth-child(2),
  .zone-table td:nth-child(2) {
    display: none;
  }
}