:root { --ink:#17201b; --muted:#657168; --paper:#f6f3ec; --surface:#fffdf8; --forest:#123b2d; --leaf:#dce7c9; --line:#d9d5ca; --accent:#d85c35; --shadow:0 18px 45px rgba(30,43,34,.09); }
* { box-sizing:border-box; }
html { scroll-behavior:smooth; }
body { margin:0; background:var(--paper); color:var(--ink); font-family:Georgia,"Noto Serif SC","Songti SC",serif; line-height:1.55; }
a { color:inherit; } button, input { font:inherit; }
.skip-link { position:absolute; left:-999px; top:0; z-index:99; background:var(--forest); color:#fff; padding:10px 14px; }.skip-link:focus { left:10px; top:10px; }
.site-header, .content-header { min-height:70px; padding:0 max(24px, calc((100vw - 1220px) / 2)); display:flex; align-items:center; justify-content:space-between; border-bottom:1px solid var(--line); background:rgba(246,243,236,.93); backdrop-filter:blur(12px); }
.site-header { position:sticky; top:0; z-index:20; }.content-header { position:relative; z-index:5; }
.brand { display:inline-flex; gap:10px; align-items:center; text-decoration:none; font-family:Arial,sans-serif; font-size:16px; font-weight:800; letter-spacing:.025em; }.brand span { display:grid; place-items:center; width:31px; height:31px; border-radius:50%; background:var(--forest); color:#fff; font-size:11px; letter-spacing:.06em; }
.top-nav, .content-actions { display:flex; align-items:center; gap:22px; font-family:Arial,sans-serif; font-size:14px; }.top-nav a, .content-actions a { text-decoration:none; }.top-nav a:hover, .content-actions a:hover { color:var(--accent); }
.language-switch { display:flex; padding-left:9px; border-left:1px solid var(--line); }.lang-button { min-width:30px; padding:6px 5px; border:0; background:transparent; color:var(--muted); cursor:pointer; font:700 11px Arial,sans-serif; }.lang-button.is-active { color:var(--forest); text-decoration:underline; text-underline-offset:4px; }
main { max-width:1220px; padding:0 24px; margin:auto; }.hero { min-height:510px; display:grid; grid-template-columns:minmax(0,1.55fr) minmax(300px,.72fr); align-items:center; gap:70px; padding:72px 0 64px; }
.eyebrow, .card-kicker { margin:0 0 14px; font-family:Arial,sans-serif; color:var(--accent); font-size:11px; letter-spacing:.14em; font-weight:800; }.hero h1 { margin:0; max-width:780px; color:var(--forest); font-size:clamp(39px,5.5vw,76px); line-height:1.09; font-weight:700; letter-spacing:-.055em; }.hero-text { max-width:650px; margin:27px 0 30px; color:var(--muted); font-size:18px; }
.hero-actions, .card-actions { display:flex; gap:12px; flex-wrap:wrap; }.button { display:inline-flex; align-items:center; justify-content:center; min-height:45px; padding:10px 18px; text-decoration:none; font-family:Arial,sans-serif; font-weight:700; font-size:14px; border:1px solid var(--forest); transition:transform .16s ease, box-shadow .16s ease; }.button:hover { transform:translateY(-2px); box-shadow:0 8px 18px rgba(18,59,45,.15); }.button-primary { background:var(--forest); color:#fff; }.button-secondary { background:transparent; color:var(--forest); }
.study-map { padding:27px 30px; border:1px solid #b9c8b4; background:var(--leaf); box-shadow:var(--shadow); }.panel-label { margin:0 0 8px; color:var(--forest); font:800 11px Arial,sans-serif; letter-spacing:.1em; }.map-item { display:grid; grid-template-columns:57px 1fr; gap:12px; padding:12px 0; border-top:1px solid rgba(18,59,45,.16); }.map-item strong { color:var(--forest); font:800 29px/1 Arial,sans-serif; letter-spacing:-.07em; }.map-item span { align-self:center; color:#365047; font-size:14px; }.map-note { margin:13px 0 0; color:#365047; font-size:14px; }
.how-it-works { display:grid; grid-template-columns:repeat(3,1fr); border-top:1px solid var(--line); border-bottom:1px solid var(--line); }.how-it-works article { min-height:190px; padding:30px 32px 30px 0; border-right:1px solid var(--line); }.how-it-works article + article { padding-left:32px; }.how-it-works article:last-child { border:0; }.how-it-works span { color:var(--accent); font:800 12px Arial,sans-serif; letter-spacing:.1em; }.how-it-works h2 { margin:23px 0 8px; color:var(--forest); font-size:24px; letter-spacing:-.035em; }.how-it-works p { margin:0; color:var(--muted); font-size:15px; }
.library-section, .exam-section { padding:103px 0; }.exam-section { border-top:1px solid var(--line); }.section-heading { display:flex; justify-content:space-between; gap:30px; margin-bottom:35px; }.section-heading h2 { margin:0 0 7px; color:var(--forest); font-size:42px; line-height:1.1; letter-spacing:-.045em; }.section-heading p:not(.eyebrow) { margin:0; color:var(--muted); }.library-tools { width:min(100%, 440px); align-self:flex-end; }.search input { width:100%; padding:11px 13px; border:1px solid var(--line); background:var(--surface); outline-color:var(--forest); font-size:14px; }.filters { display:flex; gap:7px; margin-top:12px; }.filter { border:1px solid var(--line); padding:7px 12px; color:var(--muted); background:transparent; cursor:pointer; font:700 13px Arial,sans-serif; }.filter.is-active { color:#fff; border-color:var(--forest); background:var(--forest); }
.lesson-grid { display:grid; grid-template-columns:repeat(3,1fr); gap:14px; }.lesson-card { display:flex; flex-direction:column; min-height:265px; padding:22px; border:1px solid var(--line); background:var(--surface); transition:border-color .16s ease, transform .16s ease; }.lesson-card:hover { transform:translateY(-3px); border-color:#9aad9f; }.lesson-card-top { display:flex; justify-content:space-between; font:700 12px Arial,sans-serif; }.lesson-number { color:var(--accent); letter-spacing:.08em; }.lesson-category { color:var(--muted); }.lesson-card h3 { margin:25px 0 7px; color:var(--forest); font:700 30px/1 Arial,sans-serif; letter-spacing:-.06em; }.lesson-card p { min-height:49px; margin:0; font-size:17px; line-height:1.45; }.lesson-card small { margin-top:8px; color:var(--muted); font-size:13px; }.card-actions { margin-top:auto; padding-top:23px; font:700 13px Arial,sans-serif; }.card-actions a { text-decoration:none; color:var(--forest); }.card-actions .answer-link { color:var(--muted); font-weight:600; }.empty-state { padding:28px; text-align:center; color:var(--muted); border:1px dashed var(--line); }
.exam-grid { display:grid; grid-template-columns:repeat(2,1fr); gap:16px; }.exam-card { padding:35px; min-height:350px; }.student-card { background:var(--forest); color:#fff; }.key-card { border:1px solid #b9c8b4; background:var(--leaf); }.exam-card h3 { margin:0 0 14px; font-size:37px; letter-spacing:-.05em; }.exam-card p:not(.card-kicker) { max-width:390px; margin:0; }.student-card .card-kicker { color:#e6c7a4; }.exam-card ul { padding-left:19px; margin:25px 0; font-size:15px; }.exam-card .button { margin-top:8px; }.student-card .button-primary { color:var(--forest); border-color:#fff; background:#fff; }.site-footer { display:flex; justify-content:space-between; gap:18px; max-width:1220px; margin:auto; padding:24px; border-top:1px solid var(--line); color:var(--muted); font:13px Arial,sans-serif; }.site-footer span:first-child { color:var(--forest); font-weight:800; }.site-footer a { color:var(--forest); text-decoration:none; }
.content-intro { background:var(--forest); color:#fff; }.content-intro-inner { max-width:1180px; min-height:180px; padding:35px 24px; margin:auto; display:flex; justify-content:space-between; align-items:flex-end; gap:30px; }.content-intro .eyebrow { color:#e6c7a4; }.content-intro h1 { margin:0 0 8px; max-width:800px; font-size:clamp(29px,4vw,48px); line-height:1.1; letter-spacing:-.045em; }.content-intro p:not(.eyebrow) { max-width:740px; margin:0; color:#d1ddd4; }.content-mode { flex:none; padding:7px 10px; border:1px solid rgba(255,255,255,.5); font:700 11px Arial,sans-serif; letter-spacing:.08em; text-transform:uppercase; }.learning-nav { background:var(--surface); border-bottom:1px solid var(--line); }.learning-nav.is-empty { display:none; }.learning-nav-inner { max-width:1180px; min-height:58px; margin:auto; padding:8px 24px; display:grid; grid-template-columns:1fr auto 1fr; align-items:center; gap:15px; font:700 13px Arial,sans-serif; }.learning-nav-inner > :last-child { text-align:right; }.learning-nav a { color:var(--forest); text-decoration:none; }.learning-nav .switch-link { padding:8px 12px; border:1px solid var(--forest); }.document-shell { max-width:100%; padding:38px 24px 70px; overflow:hidden; }.sr-only { position:absolute; width:1px; height:1px; padding:0; margin:-1px; overflow:hidden; clip:rect(0,0,0,0); white-space:nowrap; border:0; }
@media (max-width:780px) { .site-header, .content-header { min-height:61px; padding:0 16px; }.top-nav a { display:none; }.content-context { display:none; }.content-actions { gap:10px; }.home-link { font-size:12px; }.hero { grid-template-columns:1fr; gap:32px; min-height:auto; padding:55px 0; }.hero h1 { font-size:45px; }.hero-text { font-size:16px; }.how-it-works { grid-template-columns:1fr; }.how-it-works article, .how-it-works article + article { min-height:auto; padding:24px 0; border-right:0; border-bottom:1px solid var(--line); }.how-it-works article:last-child { border-bottom:0; }.library-section, .exam-section { padding:68px 0; }.section-heading { flex-direction:column; }.section-heading h2 { font-size:35px; }.library-tools { width:100%; }.lesson-grid, .exam-grid { grid-template-columns:1fr; }.lesson-card { min-height:225px; }.exam-card { min-height:auto; padding:27px; }.exam-card h3 { font-size:31px; }.site-footer { flex-direction:column; }.content-intro-inner { min-height:150px; padding:28px 16px; align-items:flex-start; flex-direction:column; gap:15px; }.learning-nav-inner { padding:8px 16px; }.learning-nav-inner span { display:none; }.learning-nav .switch-link { padding:7px; font-size:12px; }.document-shell { padding:16px 0 40px; } }
@media print { .content-header, .content-intro, .learning-nav, .skip-link { display:none !important; }.document-shell { padding:0 !important; } }
@media (prefers-reduced-motion:reduce) { *, *::before, *::after { scroll-behavior:auto !important; transition:none !important; } }

/* Shared lesson masthead: one continuous identity block for every generated page. */
.content-masthead { position:relative; overflow:hidden; color:#fff; background:linear-gradient(118deg, #0d3024 0%, #164b38 58%, #1d5841 100%); }
.content-masthead::after { content:""; position:absolute; right:-10vw; top:-32vw; width:60vw; height:60vw; border:1px solid rgba(226,198,157,.2); border-radius:50%; pointer-events:none; }
.content-masthead .content-header { position:relative; z-index:1; min-height:66px; border-bottom:1px solid rgba(255,255,255,.14); background:transparent; backdrop-filter:none; }
.content-masthead .brand { color:#fff; }.content-masthead .brand span { color:var(--forest); background:#e6c69d; }
.content-masthead .content-actions { gap:16px; }.content-masthead .home-link { padding:7px 10px; border:1px solid rgba(255,255,255,.38); color:#fff; font-size:12px; }.content-masthead .home-link:hover { border-color:#e6c69d; color:#e6c69d; }
.content-masthead .language-switch { border-left-color:rgba(255,255,255,.25); }.content-masthead .lang-button { color:#c9d8cf; }.content-masthead .lang-button.is-active { color:#fff; }
.content-intro { position:relative; z-index:1; background:transparent; }.content-intro-inner { max-width:1180px; min-height:176px; padding:32px 24px 34px; margin:auto; display:flex; justify-content:space-between; align-items:flex-end; gap:28px; }.content-identity { display:flex; align-items:flex-start; gap:20px; }.content-index { display:grid; flex:none; place-items:center; width:54px; height:54px; margin-top:2px; border:1px solid rgba(230,198,157,.7); color:#e6c69d; font:800 16px Arial,sans-serif; letter-spacing:.04em; }.content-intro .eyebrow { margin-bottom:8px; color:#e6c69d; }.content-intro h1 { margin:0 0 7px; max-width:800px; font-size:clamp(29px,4vw,48px); line-height:1.1; letter-spacing:-.045em; }.content-intro p:not(.eyebrow) { max-width:740px; margin:0; color:#d1ddd4; }.content-mode { flex:none; padding:8px 11px; border:1px solid rgba(230,198,157,.75); color:#fff0d6; font:700 11px Arial,sans-serif; letter-spacing:.09em; text-transform:uppercase; }
.content-masthead .learning-nav { position:relative; z-index:1; background:rgba(4,28,20,.28); border-top:1px solid rgba(255,255,255,.14); border-bottom:0; }.content-masthead .learning-nav a { color:#fff; }.content-masthead .learning-nav a:hover { color:#e6c69d; }.content-masthead .learning-nav .switch-link { border-color:#e6c69d; color:#fff0d6; }.content-masthead .learning-nav .switch-link:hover { color:var(--forest); background:#e6c69d; }.content-masthead .learning-nav.is-empty { display:none; }
/* Source exercise files contain global red heading rules; never let them leak into the dark masthead. */
.content-masthead, .content-masthead h1, .content-masthead h2, .content-masthead h3, .content-masthead h4 { color:#fff !important; }.content-masthead .content-intro h1 { color:#fff !important; }.content-masthead .content-intro p:not(.eyebrow) { color:#dbe7df !important; }.content-masthead .content-intro .eyebrow, .content-masthead .content-index { color:#f0d29e !important; }
@media (max-width:780px) { .content-masthead .content-header { min-height:61px; }.content-masthead .content-intro-inner { min-height:148px; padding:27px 16px 29px; align-items:flex-start; flex-direction:column; gap:14px; }.content-identity { gap:13px; }.content-index { width:42px; height:42px; font-size:13px; }.content-intro h1 { font-size:31px; }.content-mode { margin-left:55px; }.content-masthead .learning-nav-inner { min-height:54px; }.content-masthead .home-link { padding:6px 8px; } }
@media print { .content-masthead { display:none !important; } }