.os-hero {
    position: relative;
    overflow: hidden;
    padding: 76px 0 70px;
    background: var(--paper-bright);
}
.os-hero::after {
    content: "";
    position: absolute;
    top: -260px;
    right: -180px;
    width: 620px;
    height: 620px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(212,175,55,.16), transparent 68%);
    pointer-events: none;
}
.os-hero-grid { position: relative; z-index: 2; display: grid; grid-template-columns: minmax(0,1.05fr) minmax(390px,.75fr); align-items: center; gap: 58px; }
.os-hero-copy .lead { max-width: 720px; margin-bottom: 28px; }
.os-definition-card { padding: 32px; background: #fff; border: 1px solid var(--line); border-radius: var(--radius-lg); box-shadow: var(--shadow); }
.os-definition-card h2 { margin: 10px 0 14px; font-size: clamp(28px,3vw,40px); }
.os-definition-card p { margin-bottom: 22px; color: var(--muted); }
.os-card-kicker { color: var(--gold-deep); font-size: 11px; font-weight: 900; letter-spacing: .14em; text-transform: uppercase; }
.os-definition-tags { display: flex; flex-wrap: wrap; gap: 8px; }
.os-definition-tags span { padding: 8px 11px; background: #f5efe1; border: 1px solid #e3d7ba; border-radius: 999px; font-size: 12px; font-weight: 800; }

.os-ribbon { color: #fff; background: var(--ink); border-top: 1px solid #2c281c; border-bottom: 1px solid #2c281c; }
.os-ribbon-grid { min-height: 88px; display: grid; grid-template-columns: repeat(5,1fr); align-items: stretch; }
.os-ribbon-grid div { display: grid; grid-template-columns: auto 1fr; align-items: center; gap: 10px; padding: 16px 18px; border-right: 1px solid #343126; }
.os-ribbon-grid div:last-child { border-right: 0; }
.os-ribbon-grid strong { color: var(--gold-soft); font-size: 12px; letter-spacing: .13em; }
.os-ribbon-grid span { color: #ddd7ca; font-size: 13px; font-weight: 800; }

.os-intro-grid { display: grid; grid-template-columns: minmax(0,.9fr) minmax(0,1.1fr); align-items: start; gap: 60px; }
.os-problem-list { display: grid; gap: 12px; }
.os-problem-list article { display: grid; grid-template-columns: 48px 1fr; gap: 16px; padding: 20px; background: #fff; border: 1px solid var(--line); border-radius: var(--radius-md); }
.os-problem-list article > span { display: grid; width: 42px; height: 42px; place-items: center; color: var(--ink); background: var(--gold-soft); border-radius: 50%; font-size: 12px; font-weight: 900; }
.os-problem-list h3 { margin-bottom: 5px; font-size: 18px; }
.os-problem-list p { margin: 0; color: var(--muted); font-size: 14px; }

.os-dark-heading { display: flex; justify-content: space-between; align-items: end; gap: 46px; margin-bottom: 34px; }
.os-dark-heading .lead { color: #aaa497; }
.os-function-grid { display: grid; grid-template-columns: repeat(3,1fr); border: 1px solid #343126; border-radius: var(--radius-lg); overflow: hidden; }
.os-function-grid article { min-height: 224px; padding: 30px; background: #0d0d0c; border-right: 1px solid #343126; border-bottom: 1px solid #343126; }
.os-function-grid article:nth-child(3n) { border-right: 0; }
.os-function-grid article:nth-child(n+4) { border-bottom: 0; }
.os-function-grid h3 { color: #fff; }
.os-function-grid p { margin-bottom: 0; color: #aaa497; font-size: 14px; }
.os-function-number { display: inline-flex; margin-bottom: 30px; color: var(--gold-soft); font-size: 11px; font-weight: 900; letter-spacing: .14em; }

.os-journey { display: grid; grid-template-columns: repeat(5,1fr); margin-top: 34px; border: 1px solid var(--line); border-radius: var(--radius-lg); overflow: hidden; background: #fff; box-shadow: var(--shadow); }
.os-journey article { position: relative; min-height: 238px; padding: 28px 24px; border-right: 1px solid var(--line); }
.os-journey article:last-child { border-right: 0; }
.os-journey article:not(:last-child)::after { content: "→"; position: absolute; top: 26px; right: -11px; z-index: 2; display: grid; width: 22px; height: 22px; place-items: center; color: var(--ink); background: var(--gold); border-radius: 50%; font-size: 12px; font-weight: 900; }
.os-journey article > span { display: grid; width: 38px; height: 38px; margin-bottom: 42px; place-items: center; color: var(--ink); background: #f1e4b8; border-radius: 50%; font-size: 12px; font-weight: 900; }
.os-journey h3 { font-size: 18px; }
.os-journey p { margin: 0; color: var(--muted); font-size: 13px; }

.os-architecture-grid { display: grid; grid-template-columns: minmax(0,.92fr) minmax(420px,1.08fr); align-items: center; gap: 64px; }
.os-body-copy { max-width: 720px; color: var(--muted); }
.os-stack { display: grid; gap: 10px; }
.os-stack div { display: grid; grid-template-columns: 92px 170px 1fr; align-items: center; gap: 18px; padding: 20px 22px; background: #fff; border: 1px solid var(--line); border-radius: 16px; box-shadow: 0 9px 25px rgba(22,18,8,.05); }
.os-stack div:first-child { border-color: #c7a233; }
.os-stack span { color: var(--gold-deep); font-size: 10px; font-weight: 900; letter-spacing: .12em; text-transform: uppercase; }
.os-stack strong { font-size: 16px; }
.os-stack small { color: var(--muted); font-size: 12px; }

.os-compare { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; margin-top: 32px; }
.os-compare-card { padding: 30px; border-radius: var(--radius-lg); }
.os-compare-card h3 { margin-top: 10px; font-size: 26px; }
.os-compare-card ul { margin: 22px 0 0; padding: 0; list-style: none; }
.os-compare-card li { position: relative; padding: 11px 0 11px 28px; border-top: 1px solid rgba(0,0,0,.10); font-weight: 700; }
.os-compare-card li::before { content: "✓"; position: absolute; left: 0; color: var(--gold-deep); font-weight: 900; }
.os-compare-muted { background: rgba(255,253,248,.72); border: 1px solid rgba(5,5,5,.16); }
.os-compare-dark { color: #fff; background: var(--ink); border: 1px solid #2e291d; box-shadow: 0 22px 48px rgba(57,40,4,.18); }
.os-compare-dark .os-card-kicker { color: var(--gold-soft); }
.os-compare-dark li { color: #d5cfc2; border-color: #343126; }
.os-compare-dark li::before { color: var(--gold-soft); }

.os-audience-grid { display: grid; grid-template-columns: minmax(0,.95fr) minmax(0,1.05fr); align-items: center; gap: 60px; }
.os-audience-list { display: grid; grid-template-columns: repeat(2,1fr); gap: 10px; }
.os-audience-list span { padding: 17px 18px; background: #fff; border: 1px solid var(--line); border-radius: 14px; font-size: 14px; font-weight: 800; }

.os-principle-grid { display: grid; grid-template-columns: repeat(4,1fr); gap: 14px; margin-top: 34px; }
.os-principle-grid article { padding: 26px; background: #0d0d0c; border: 1px solid #343126; border-radius: var(--radius-md); }
.os-principle-grid strong { display: inline-flex; margin-bottom: 34px; color: var(--gold-soft); font-size: 12px; letter-spacing: .14em; }
.os-principle-grid h3 { color: #fff; font-size: 19px; }
.os-principle-grid p { margin: 0; color: #aaa497; font-size: 13px; }

.os-faq-grid { display: grid; grid-template-columns: minmax(0,.75fr) minmax(0,1.25fr); align-items: start; gap: 60px; }
.os-faq-list { display: grid; gap: 10px; }
.os-faq-list details { overflow: hidden; background: #fff; border: 1px solid var(--line); border-radius: 14px; }
.os-faq-list summary { position: relative; display: flex; justify-content: space-between; gap: 20px; padding: 18px 20px; cursor: pointer; list-style: none; font-weight: 900; }
.os-faq-list summary::-webkit-details-marker { display: none; }
.os-faq-list summary span { color: var(--gold-deep); font-size: 20px; line-height: 1; transition: transform .18s ease; }
.os-faq-list details[open] summary span { transform: rotate(45deg); }
.os-faq-list details p { margin: 0; padding: 0 20px 20px; color: var(--muted); font-size: 14px; }

@media (max-width: 1080px) {
    .os-hero-grid { grid-template-columns: 1fr 390px; gap: 36px; }
    .os-journey { grid-template-columns: repeat(3,1fr); }
    .os-journey article { border-bottom: 1px solid var(--line); }
    .os-journey article:nth-child(3) { border-right: 0; }
    .os-journey article:nth-child(3)::after { display: none; }
    .os-journey article:nth-child(n+4) { border-bottom: 0; }
    .os-principle-grid { grid-template-columns: repeat(2,1fr); }
}

@media (max-width: 980px) {
    .os-hero-grid, .os-intro-grid, .os-architecture-grid, .os-audience-grid, .os-faq-grid { grid-template-columns: 1fr; }
    .os-definition-card { max-width: 720px; }
    .os-ribbon-grid { grid-template-columns: repeat(3,1fr); }
    .os-ribbon-grid div:nth-child(3) { border-right: 0; }
    .os-ribbon-grid div:nth-child(n+4) { border-top: 1px solid #343126; }
    .os-dark-heading { display: block; }
    .os-function-grid { grid-template-columns: repeat(2,1fr); }
    .os-function-grid article:nth-child(3n) { border-right: 1px solid #343126; }
    .os-function-grid article:nth-child(2n) { border-right: 0; }
    .os-function-grid article:nth-child(n+4) { border-bottom: 1px solid #343126; }
    .os-function-grid article:nth-child(n+5) { border-bottom: 0; }
    .os-stack div { grid-template-columns: 84px 150px 1fr; }
}

@media (max-width: 720px) {
    .os-hero { padding: 48px 0 44px; }
    .os-definition-card { padding: 22px; border-radius: 22px; }
    .os-ribbon-grid { grid-template-columns: 1fr; padding: 8px 0; }
    .os-ribbon-grid div, .os-ribbon-grid div:nth-child(3), .os-ribbon-grid div:nth-child(n+4) { min-height: 54px; border-right: 0; border-top: 1px solid #343126; }
    .os-ribbon-grid div:first-child { border-top: 0; }
    .os-problem-list article { grid-template-columns: 40px 1fr; padding: 17px; }
    .os-problem-list article > span { width: 36px; height: 36px; }
    .os-function-grid { grid-template-columns: 1fr; border-radius: 22px; }
    .os-function-grid article, .os-function-grid article:nth-child(3n), .os-function-grid article:nth-child(2n), .os-function-grid article:nth-child(n+4), .os-function-grid article:nth-child(n+5) { min-height: 0; border-right: 0; border-bottom: 1px solid #343126; }
    .os-function-grid article:last-child { border-bottom: 0; }
    .os-function-number { margin-bottom: 20px; }
    .os-journey { grid-template-columns: 1fr; border-radius: 22px; }
    .os-journey article, .os-journey article:nth-child(3), .os-journey article:nth-child(n+4) { min-height: 0; border-right: 0; border-bottom: 1px solid var(--line); }
    .os-journey article:last-child { border-bottom: 0; }
    .os-journey article:not(:last-child)::after { top: auto; right: 24px; bottom: -11px; content: "↓"; }
    .os-journey article:nth-child(3)::after { display: grid; }
    .os-journey article > span { margin-bottom: 24px; }
    .os-stack div { grid-template-columns: 1fr; gap: 4px; padding: 18px; }
    .os-compare { grid-template-columns: 1fr; }
    .os-audience-list { grid-template-columns: 1fr; }
    .os-principle-grid { grid-template-columns: 1fr; }
}