:root {
  --bg: #F5F5F7;
  --card: #FFFFFF;
  --text: #1C1C1E;
  --text-2: #6E6E73;
  --hairline: rgba(0, 0, 0, 0.08);
  --accent: #007AFF;
  --accent-soft: rgba(0, 122, 255, 0.08);
  --danger: #FF3B30;
  --radius-card: 20px;
  --radius-control: 14px;
  --shadow-soft: 0 8px 24px rgba(0, 0, 0, 0.08);
  --ease-in: cubic-bezier(0.32, 0.72, 0, 1);
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000000;
    --card: #1C1C1E;
    --text: #F5F5F7;
    --text-2: #98989D;
    --hairline: rgba(255, 255, 255, 0.12);
    --accent: #0A84FF;
    --accent-soft: rgba(10, 132, 255, 0.16);
    --shadow-soft: 0 8px 24px rgba(0, 0, 0, 0.4);
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, "SF Pro Display", "PingFang SC", "Helvetica Neue", sans-serif;
  font-size: 17px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

.num {
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum";
}

.wrap {
  max-width: 640px;
  margin: 0 auto;
  padding: 20px 20px 80px;
}

/* ---------- Header ---------- */

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 0 24px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text);
  text-decoration: none;
}

.brand svg { display: block; }

.header-link {
  font-size: 15px;
  color: var(--accent);
  text-decoration: none;
  padding: 8px 4px;
}

/* ---------- Type ---------- */

.eyebrow {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 8px;
}

h1 {
  font-size: 34px;
  line-height: 1.15;
  letter-spacing: -0.02em;
  font-weight: 700;
  margin: 0 0 12px;
}

h2 {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 48px 0 8px;
}

h3 {
  font-size: 17px;
  font-weight: 600;
  margin: 0 0 6px;
}

.lede {
  color: var(--text-2);
  margin: 0 0 24px;
  max-width: 34ch;
}

.section-sub {
  color: var(--text-2);
  margin: 0 0 16px;
  font-size: 15px;
}

.caption {
  font-size: 13px;
  color: var(--text-2);
  margin: 12px 0 0;
}

/* ---------- Cards ---------- */

.card {
  background: var(--card);
  border: 0.5px solid var(--hairline);
  border-radius: var(--radius-card);
  padding: 20px;
  margin: 0 0 16px;
}

.card.flat {
  box-shadow: none;
}

/* ---------- Calculator ---------- */

.field {
  margin: 0 0 16px;
}

.field label {
  display: block;
  font-size: 15px;
  font-weight: 600;
  margin: 0 0 8px;
}

.field .hint {
  display: block;
  font-weight: 400;
  font-size: 13px;
  color: var(--text-2);
  margin-top: 4px;
}

.field input {
  width: 100%;
  min-height: 48px;
  font-size: 17px;
  font-family: inherit;
  color: var(--text);
  background: var(--bg);
  border: 0.5px solid var(--hairline);
  border-radius: var(--radius-control);
  padding: 12px 16px;
  appearance: none;
}

.field input:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: transparent;
}

.field input[aria-invalid="true"] {
  border-color: var(--danger);
}

.field-error {
  display: none;
  font-size: 13px;
  color: var(--danger);
  margin: 6px 0 0;
}

.field-error.show { display: block; }

.optional-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

@media (max-width: 360px) {
  .optional-grid { grid-template-columns: 1fr; }
}

.btn {
  display: block;
  width: 100%;
  min-height: 52px;
  border: 0;
  border-radius: var(--radius-control);
  background: var(--accent);
  color: #fff;
  font-family: inherit;
  font-size: 17px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 200ms var(--ease-in), opacity 200ms;
}

.btn:active { transform: scale(0.98); }

.example-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  margin-top: 16px;
  font-size: 15px;
  color: var(--text-2);
}

.link-btn {
  background: none;
  border: 0;
  padding: 10px 6px;
  font-family: inherit;
  font-size: 15px;
  font-weight: 600;
  color: var(--accent);
  cursor: pointer;
}

/* ---------- Results ---------- */

#results { scroll-margin-top: 16px; }

.results-enter {
  animation: rise 240ms var(--ease-in);
}

@keyframes rise {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

.hero-card {
  text-align: center;
  padding: 32px 20px;
  box-shadow: var(--shadow-soft);
}

.hero-label {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-2);
  margin: 0 0 8px;
}

.hero-number {
  font-size: 34px;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--accent);
  margin: 0;
}

.hero-unit {
  font-size: 15px;
  color: var(--text-2);
  margin: 8px 0 0;
}

.hero-secondary {
  margin-top: 16px;
  padding-top: 16px;
  border-top: 0.5px solid var(--hairline);
  font-size: 15px;
  color: var(--text-2);
}

.hero-secondary strong { color: var(--text); font-weight: 600; }

.basis-note {
  margin-top: 12px;
  font-size: 13px;
  color: var(--text-2);
}

.method-card .method-tag {
  display: inline-block;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-soft);
  border-radius: 999px;
  padding: 4px 10px;
  margin-bottom: 10px;
}

.method-card p {
  font-size: 15px;
  color: var(--text-2);
  margin: 0 0 12px;
}

.method-range {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0;
}

.method-range .unit {
  font-size: 13px;
  font-weight: 400;
  color: var(--text-2);
}

.method-empty {
  border: 1px dashed var(--hairline);
  border-radius: var(--radius-control);
  padding: 16px;
  font-size: 15px;
  color: var(--text-2);
  text-align: center;
}

.method-empty strong { color: var(--text); }

/* ---------- Zone table ---------- */

.zone-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 15px;
}

.zone-table th {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-2);
  text-align: left;
  padding: 8px 12px;
  border-bottom: 0.5px solid var(--hairline);
}

.zone-table td {
  padding: 12px;
  border-bottom: 0.5px solid var(--hairline);
}

.zone-table tr:last-child td { border-bottom: 0; }

.zone-table tr.hl td {
  background: var(--accent-soft);
}

.zone-table tr.hl td:first-child { border-radius: 12px 0 0 12px; }
.zone-table tr.hl td:last-child { border-radius: 0 12px 12px 0; }

.zone-table .zname { font-weight: 600; }
.zone-table .zname small {
  display: block;
  font-weight: 400;
  font-size: 13px;
  color: var(--text-2);
}

/* ---------- Plan / sport cards ---------- */

.plan-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}

.plan-card {
  background: var(--card);
  border: 0.5px solid var(--hairline);
  border-radius: var(--radius-card);
  padding: 20px;
}

.plan-card .sessions {
  font-size: 28px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0 0 4px;
}

.plan-card p {
  font-size: 15px;
  color: var(--text-2);
  margin: 0;
}

.plan-card .tag {
  display: inline-block;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 8px;
}

.sport-list { list-style: none; margin: 0; padding: 0; }

.sport-list li {
  display: flex;
  gap: 12px;
  padding: 16px 0;
  border-bottom: 0.5px solid var(--hairline);
}

.sport-list li:last-child { border-bottom: 0; padding-bottom: 0; }
.sport-list li:first-child { padding-top: 0; }

.sport-list .icon {
  flex: 0 0 40px;
  width: 40px;
  height: 40px;
  border-radius: 12px;
  background: var(--accent-soft);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent);
}

.sport-list .body p {
  font-size: 15px;
  color: var(--text-2);
  margin: 4px 0 0;
}

/* ---------- Info / FAQ / footer ---------- */

.info-list { margin: 0 0 16px; padding: 0; list-style: none; }

.info-list li {
  font-size: 15px;
  color: var(--text-2);
  padding: 12px 0;
  border-bottom: 0.5px solid var(--hairline);
}

.info-list li:last-child { border-bottom: 0; }
.info-list li strong { color: var(--text); font-weight: 600; }

details.faq {
  background: var(--card);
  border: 0.5px solid var(--hairline);
  border-radius: var(--radius-card);
  margin: 0 0 12px;
  overflow: hidden;
}

details.faq summary {
  list-style: none;
  cursor: pointer;
  padding: 18px 20px;
  font-size: 17px;
  font-weight: 600;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

details.faq summary::-webkit-details-marker { display: none; }

details.faq summary .chev {
  flex: 0 0 auto;
  color: var(--text-2);
  transition: transform 200ms var(--ease-in);
}

details.faq[open] summary .chev { transform: rotate(180deg); }

details.faq .faq-body {
  padding: 0 20px 20px;
  font-size: 15px;
  color: var(--text-2);
}

details.faq .faq-body p { margin: 0 0 12px; }
details.faq .faq-body p:last-child { margin-bottom: 0; }

.cta-card {
  text-align: center;
  padding: 28px 20px;
}

.cta-card .btn {
  max-width: 280px;
  margin: 16px auto 0;
}

.site-footer {
  margin-top: 56px;
  padding-top: 24px;
  border-top: 0.5px solid var(--hairline);
  font-size: 13px;
  color: var(--text-2);
}

.site-footer p { margin: 0 0 12px; }

.site-footer .disclaimer strong { color: var(--text); }

.footer-nav {
  display: flex;
  gap: 20px;
  margin-top: 16px;
  padding-bottom: 8px;
}

.footer-nav a {
  color: var(--accent);
  text-decoration: none;
  font-size: 15px;
  padding: 8px 0;
}

/* ---------- Age table page ---------- */

.age-table { width: 100%; border-collapse: collapse; font-size: 15px; }

.age-table th {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-2);
  text-align: left;
  padding: 10px 12px;
  border-bottom: 0.5px solid var(--hairline);
  position: sticky;
  top: 0;
  background: var(--card);
}

.age-table td {
  padding: 12px;
  border-bottom: 0.5px solid var(--hairline);
}

.age-table tr:last-child td { border-bottom: 0; }
.age-table .z2 { font-weight: 700; color: var(--accent); }

/* ---------- Motion safety ---------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .results-enter { animation: none; }
  .btn { transition: none; }
  details.faq summary .chev { transition: none; }
}