/* =========================================================================
   OptionsGyan — global styles
   ========================================================================= */
:root {
  --bg: #f7f8fb;
  --surface: #ffffff;
  --surface-2: #f0f2f7;
  --border: #e2e6ef;
  --text: #14181f;
  --text-soft: #4c5666;
  --text-mute: #8a93a6;
  --brand: #0b5d4e;      /* deep teal-green */
  --brand-soft: #e6f2ee;
  --accent: #c9922b;     /* muted gold */
  --bull: #10916d;
  --bear: #d1435b;
  --neutral: #6b74c4;
  --vol: #b5642a;
  --shadow: 0 1px 2px rgba(17,24,39,.04), 0 8px 24px rgba(17,24,39,.06);
  --radius: 14px;
  --maxw: 1120px;
  --font: "Segoe UI", system-ui, -apple-system, Roboto, Helvetica, Arial, sans-serif;
  --serif: Georgia, "Times New Roman", serif;
}
/* dark palette — applied when the user forces dark, OR when the system is dark
   and the user has NOT forced light. The [data-theme] toggle always wins. */
:root[data-theme="dark"] {
  --bg: #0d1017; --surface: #151a23; --surface-2: #1c222e; --border: #262d3b;
  --text: #eef1f6; --text-soft: #b3bccb; --text-mute: #7b8598;
  --brand: #3bb890; --brand-soft: #12241e; --accent: #e0b055;
  --shadow: 0 1px 2px rgba(0,0,0,.3), 0 10px 30px rgba(0,0,0,.35);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0d1017; --surface: #151a23; --surface-2: #1c222e; --border: #262d3b;
    --text: #eef1f6; --text-soft: #b3bccb; --text-mute: #7b8598;
    --brand: #3bb890; --brand-soft: #12241e; --accent: #e0b055;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 10px 30px rgba(0,0,0,.35);
  }
}
html { color-scheme: light dark; }
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font-family: var(--font); line-height: 1.6; font-size: 16px;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }
img, svg { max-width: 100%; }
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

/* ---------- Header / Nav ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--border);
}
.nav {
  display: flex; align-items: center; gap: 18px;
  height: 62px;
}
.brand {
  display: flex; align-items: center; gap: 10px;
  font-weight: 800; font-size: 1.15rem; color: var(--text); letter-spacing: -.02em;
}
.brand:hover { text-decoration: none; }
.brand .logo {
  width: 30px; height: 30px; border-radius: 8px;
  background: linear-gradient(135deg, var(--brand), var(--accent));
  display: grid; place-items: center; color: #fff; font-weight: 900;
  font-size: .95rem;
}
.brand small { color: var(--accent); font-weight: 700; }
.nav-links { display: flex; gap: 4px; margin-left: auto; align-items: center; flex-wrap: wrap; }
.nav-links a {
  color: var(--text-soft); font-weight: 600; font-size: .92rem;
  padding: 8px 12px; border-radius: 8px;
}
.nav-links a:hover { background: var(--surface-2); color: var(--text); text-decoration: none; }
.nav-toggle { display: none; background: none; border: 1px solid var(--border);
  border-radius: 8px; padding: 6px 10px; color: var(--text); font-size: 1.2rem; cursor: pointer; }
.theme-toggle {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 999px;
  width: 38px; height: 38px; display: grid; place-items: center; cursor: pointer;
  color: var(--text); font-size: 1.05rem; line-height: 1; transition: .15s; flex: none;
}
.theme-toggle:hover { border-color: var(--brand); color: var(--brand); }
.theme-toggle .sun { display: none; }
.theme-toggle .moon { display: block; }
:root[data-theme="dark"] .theme-toggle .sun { display: block; }
:root[data-theme="dark"] .theme-toggle .moon { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .theme-toggle .sun { display: block; }
  :root:not([data-theme="light"]) .theme-toggle .moon { display: none; }
}
@media (max-width: 820px) {
  .nav-toggle { display: block; margin-left: auto; }
  .nav-links { display: none; width: 100%; flex-direction: column; align-items: stretch;
    padding: 8px 0 14px; }
  .nav-links.open { display: flex; }
  .nav { flex-wrap: wrap; height: auto; padding: 10px 0; }
}

/* ---------- Hero ---------- */
.hero {
  position: relative; overflow: hidden;
  background:
    radial-gradient(1200px 500px at 80% -10%, color-mix(in srgb, var(--brand) 22%, transparent), transparent),
    radial-gradient(900px 500px at 0% 120%, color-mix(in srgb, var(--accent) 16%, transparent), transparent);
  border-bottom: 1px solid var(--border);
}
.hero-inner { padding: 74px 0 64px; max-width: 760px; }
.eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  font-size: .78rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase;
  color: var(--brand); background: var(--brand-soft);
  padding: 6px 12px; border-radius: 999px; border: 1px solid color-mix(in srgb, var(--brand) 25%, transparent);
}
.hero h1 {
  font-size: clamp(2.1rem, 5.5vw, 3.5rem); line-height: 1.08; letter-spacing: -.03em;
  margin: 18px 0 14px; font-weight: 850;
}
.hero h1 .grad {
  background: linear-gradient(120deg, var(--brand), var(--accent));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p.lead { font-size: 1.18rem; color: var(--text-soft); margin: 0 0 26px; }
.hero-cta { display: flex; gap: 12px; flex-wrap: wrap; }
.hero-stats { display: flex; gap: 30px; margin-top: 38px; flex-wrap: wrap; }
.hero-stats .stat b { display: block; font-size: 1.7rem; font-weight: 800; letter-spacing: -.02em; }
.hero-stats .stat span { color: var(--text-mute); font-size: .86rem; }

.btn {
  display: inline-flex; align-items: center; gap: 8px;
  font-weight: 700; font-size: .96rem; padding: 12px 20px; border-radius: 10px;
  border: 1px solid transparent; cursor: pointer; transition: transform .08s ease, box-shadow .2s;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn-primary { background: var(--brand); color: #fff; box-shadow: var(--shadow); }
.btn-ghost { background: var(--surface); color: var(--text); border-color: var(--border); }

/* ---------- Sections ---------- */
.section { padding: 56px 0; }
.section-head { max-width: 640px; margin-bottom: 30px; }
.section-head h2 { font-size: 1.9rem; letter-spacing: -.02em; margin: 0 0 8px; }
.section-head p { color: var(--text-soft); margin: 0; }

/* ---------- Filters ---------- */
.filters { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 22px; }
.chip {
  font-size: .84rem; font-weight: 600; padding: 7px 14px; border-radius: 999px;
  border: 1px solid var(--border); background: var(--surface); color: var(--text-soft);
  cursor: pointer; transition: .15s;
}
.chip:hover { border-color: var(--brand); color: var(--text); }
.chip.active { background: var(--brand); color: #fff; border-color: var(--brand); }

/* ---------- Strategy cards ---------- */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 18px; }
.card {
  display: flex; flex-direction: column; gap: 12px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; box-shadow: var(--shadow); transition: transform .12s ease, border-color .2s;
  position: relative;
}
.card:hover { transform: translateY(-3px); border-color: color-mix(in srgb, var(--brand) 40%, var(--border)); text-decoration: none; }
.card .card-top { display: flex; justify-content: space-between; align-items: flex-start; gap: 10px; }
.card h3 { margin: 0; font-size: 1.15rem; letter-spacing: -.01em; color: var(--text); }
.card .legs { font-size: .82rem; color: var(--text-mute); font-family: var(--serif); font-style: italic; }
.card p { margin: 0; font-size: .9rem; color: var(--text-soft); }
.card .card-foot { margin-top: auto; display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.tag {
  font-size: .72rem; font-weight: 700; padding: 4px 9px; border-radius: 6px;
  text-transform: uppercase; letter-spacing: .03em;
}
.tag.bull { background: color-mix(in srgb, var(--bull) 15%, transparent); color: var(--bull); }
.tag.bear { background: color-mix(in srgb, var(--bear) 15%, transparent); color: var(--bear); }
.tag.neutral { background: color-mix(in srgb, var(--neutral) 15%, transparent); color: var(--neutral); }
.tag.vol { background: color-mix(in srgb, var(--vol) 15%, transparent); color: var(--vol); }
.tag.diff { background: var(--surface-2); color: var(--text-mute); }
.card .arrow { color: var(--brand); font-weight: 800; }

/* ---------- Strategy detail page ---------- */
.detail-hero { background: var(--surface-2); border-bottom: 1px solid var(--border); }
.detail-hero .wrap { padding: 34px 20px 30px; }
.breadcrumb { font-size: .85rem; color: var(--text-mute); margin-bottom: 12px; }
.breadcrumb a { color: var(--text-soft); }
.detail-hero h1 { font-size: clamp(1.8rem, 4vw, 2.6rem); margin: 0 0 10px; letter-spacing: -.02em; }
.detail-tags { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 14px; }
.detail-summary { font-size: 1.12rem; color: var(--text-soft); max-width: 720px; margin: 0; }

.detail-layout { display: grid; grid-template-columns: 1fr 300px; gap: 40px; padding: 40px 0; }
@media (max-width: 900px) { .detail-layout { grid-template-columns: 1fr; } }
.detail-main h2 { font-size: 1.5rem; margin: 34px 0 12px; letter-spacing: -.01em; scroll-margin-top: 80px; }
.detail-main h2:first-child { margin-top: 0; }
.detail-main p { color: var(--text-soft); }
.detail-main ul { color: var(--text-soft); padding-left: 20px; }
.detail-main li { margin-bottom: 7px; }

.callout {
  background: var(--surface); border: 1px solid var(--border); border-left: 4px solid var(--brand);
  border-radius: 10px; padding: 16px 18px; margin: 18px 0;
}
.callout.example { border-left-color: var(--accent); }
.callout h4 { margin: 0 0 6px; font-size: .95rem; }
.callout p { margin: 0; color: var(--text-soft); font-size: .95rem; }

.metrics { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px,1fr)); gap: 12px; margin: 18px 0; }
.metric { background: var(--surface); border: 1px solid var(--border); border-radius: 10px; padding: 14px; }
.metric .k { font-size: .74rem; text-transform: uppercase; letter-spacing: .05em; color: var(--text-mute); font-weight: 700; }
.metric .v { font-size: .98rem; margin-top: 4px; font-weight: 600; }
.metric.profit .v { color: var(--bull); }
.metric.loss .v { color: var(--bear); }

/* payoff chart */
.payoff-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px; box-shadow: var(--shadow); }
.payoff-card h3 { margin: 0 0 4px; font-size: 1.05rem; }
.payoff-card .hint { font-size: .82rem; color: var(--text-mute); margin: 0 0 10px; }
.payoff-svg { width: 100%; height: auto; display: block; }
.payoff-svg text { font-family: var(--font); }
.pf-frame { fill: none; stroke: var(--border); }
.pf-grid { stroke: var(--border); stroke-dasharray: 3 4; }
.pf-zero { stroke: var(--text-mute); stroke-width: 1; }
.pf-profit { fill: var(--bull); opacity: .16; }
.pf-loss { fill: var(--bear); opacity: .16; }
.pf-line { fill: none; stroke: var(--accent); stroke-width: 2.4; stroke-linejoin: round; }
.pf-be { fill: var(--accent); }
.pf-be-tx { fill: var(--accent); font-size: 10px; font-weight: 700; }
.pf-label { fill: var(--text-mute); font-size: 11px; }

/* FAQ */
.faq details {
  border: 1px solid var(--border); border-radius: 10px; margin-bottom: 10px;
  background: var(--surface); overflow: hidden;
}
.faq summary {
  cursor: pointer; padding: 14px 16px; font-weight: 650; list-style: none;
  display: flex; justify-content: space-between; gap: 12px; align-items: center;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; font-size: 1.3rem; color: var(--brand); font-weight: 700; }
.faq details[open] summary::after { content: "\2212"; }
.faq details[open] summary { border-bottom: 1px solid var(--border); }
.faq .answer { padding: 12px 16px 16px; color: var(--text-soft); font-size: .95rem; }

/* sidebar */
.detail-side { position: sticky; top: 80px; align-self: start; display: flex; flex-direction: column; gap: 18px; }
@media (max-width: 900px) { .detail-side { position: static; } }
.toc { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; }
.toc h4 { margin: 0 0 10px; font-size: .8rem; text-transform: uppercase; letter-spacing: .05em; color: var(--text-mute); }
.toc a { display: block; padding: 5px 0; color: var(--text-soft); font-size: .9rem; }
.toc a:hover { color: var(--brand); text-decoration: none; }

.related-nav { display: flex; justify-content: space-between; gap: 12px; padding: 26px 0 10px; flex-wrap: wrap; }
.related-nav a { flex: 1; min-width: 200px; background: var(--surface); border: 1px solid var(--border);
  border-radius: 10px; padding: 14px 16px; }
.related-nav a:hover { border-color: var(--brand); text-decoration: none; }
.related-nav .dir { font-size: .78rem; color: var(--text-mute); }
.related-nav .nm { font-weight: 700; color: var(--text); }
.related-nav .next { text-align: right; }

/* ---------- Content pages (legal/info) ---------- */
.doc { max-width: 800px; margin: 0 auto; padding: 44px 20px 60px; }
.doc h1 { font-size: 2rem; letter-spacing: -.02em; margin: 0 0 6px; }
.doc .updated { color: var(--text-mute); font-size: .85rem; margin-bottom: 28px; }
.doc h2 { font-size: 1.3rem; margin: 32px 0 10px; }
.doc h3 { font-size: 1.05rem; margin: 22px 0 8px; }
.doc p, .doc li { color: var(--text-soft); }
.doc ul { padding-left: 20px; }

.notice {
  border-radius: 12px; padding: 18px 20px; margin: 22px 0;
  border: 1px solid color-mix(in srgb, var(--bear) 40%, var(--border));
  background: color-mix(in srgb, var(--bear) 8%, var(--surface));
}
.notice strong { color: var(--bear); }

/* ---------- Steps / feature strip ---------- */
.features { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px,1fr)); gap: 18px; }
.feature { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px; }
.feature .ic { width: 40px; height: 40px; border-radius: 10px; background: var(--brand-soft);
  color: var(--brand); display: grid; place-items: center; font-size: 1.3rem; margin-bottom: 12px; font-weight: 800; }
.feature h3 { margin: 0 0 6px; font-size: 1.08rem; }
.feature p { margin: 0; color: var(--text-soft); font-size: .93rem; }

/* ---------- Footer ---------- */
.site-footer { background: var(--surface); border-top: 1px solid var(--border); margin-top: 40px; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 30px; padding: 46px 0 30px; }
@media (max-width: 760px) { .footer-grid { grid-template-columns: 1fr 1fr; } }
.footer-grid h5 { font-size: .78rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-mute); margin: 0 0 12px; }
.footer-grid a { display: block; color: var(--text-soft); font-size: .9rem; padding: 4px 0; }
.footer-brand p { color: var(--text-mute); font-size: .9rem; max-width: 300px; }
.footer-bottom { border-top: 1px solid var(--border); padding: 18px 0; display: flex;
  justify-content: space-between; gap: 12px; flex-wrap: wrap; color: var(--text-mute); font-size: .82rem; }
.footer-disclaimer { background: var(--surface-2); border-top: 1px solid var(--border); }
.footer-disclaimer .wrap { padding: 16px 20px; font-size: .8rem; color: var(--text-mute); }

.empty { text-align: center; color: var(--text-mute); padding: 40px; }