*{box-sizing:border-box}body{margin:0;background:#f3f5f8;color:#233247;font:17px/1.85 system-ui,-apple-system,sans-serif}header,main,footer{max-width:1240px;margin:auto;padding:24px 32px}header{display:flex;justify-content:space-between;gap:20px;align-items:center;font-size:15px}header a:first-child{font-size:24px;font-weight:850;text-decoration:none;color:#145846}a{color:#145846}.hero{position:relative;padding:30px 36px;background:linear-gradient(110deg,#e0ede8,#edf3ed 55%,#f4f4e7);border:1px solid #d7e4da;border-radius:26px}.hero p{margin:8px 0 0;color:#526454}.eyebrow{font-size:13px;font-weight:650;color:#496652}h1{font-size:clamp(28px,4vw,42px);line-height:1.45;margin:10px 0;color:#164e40;letter-spacing:-.7px}h2{font-size:clamp(23px,2.4vw,29px);line-height:1.65;margin:14px 0 20px;letter-spacing:-.4px}p{margin:10px 0}.layout{display:grid;grid-template-columns:245px minmax(0,1fr);gap:26px;margin-top:26px;align-items:start}nav{display:grid;gap:8px;align-content:start;position:sticky;top:18px}button,textarea{font:inherit}button{cursor:pointer;border:1px solid #dbe2e9;border-radius:13px;background:white;color:#27374a;padding:12px 17px;text-align:start;line-height:1.6}button:hover:not(:disabled){border-color:#628f81;background:#f3f9f5}button:focus-visible,a:focus-visible,summary:focus-visible,textarea:focus-visible{outline:3px solid #579ed2;outline-offset:3px}button:disabled{cursor:default}.primary{background:#145846;color:white;border-color:#145846;font-weight:700}.primary:hover:not(:disabled){background:#1b6954;color:white}.primary:disabled{background:#edf1f2;color:#697782;border-color:#e0e6e9}nav button{display:flex;align-items:center;gap:12px;padding:13px;font-size:14px;text-align:right;background:transparent;border-color:transparent}.lesson-number{display:grid;place-items:center;flex-shrink:0;width:32px;height:32px;background:#fff;border:1px solid #dde5e1;border-radius:10px;color:#62746d;font-size:12px;font-weight:750}.lesson-name{line-height:1.65}.lesson-name .english-term{font-weight:500;color:#6a7c8a;font-size:12px;display:block;margin-top:1px}button[aria-current=true]{background:#fff;border-color:#c4dbd1;box-shadow:0 5px 14px #193b2910;color:#145846;font-weight:750}button[aria-current=true] .lesson-number{background:#145846;color:white;border-color:#145846}button[aria-current=true] .english-term{color:#296b58}.card{background:white;border:1px solid #e0e6ed;border-radius:24px;padding:28px;margin-bottom:22px;box-shadow:0 6px 22px #29374c04;overflow:hidden}.lesson-meta{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}.step-label{font-size:12px;font-weight:750;letter-spacing:.2px;color:#276553;background:#eaf3ef;border-radius:7px;padding:4px 10px;display:inline-block}.page-label{font-size:12px;color:#76828f}.english-term{unicode-bidi:isolate;font-weight:650;color:#245f87}.lesson-intro{color:#647081;font-size:16px;margin-bottom:20px}.rule-list{list-style:none;padding:0;display:grid;gap:12px;margin:18px 0 24px}.rule-list li{position:relative;padding:14px 40px 14px 18px;background:#f6f8fb;border-radius:12px;font-size:16px}.rule-list li:before{content:'';position:absolute;right:18px;top:27px;width:7px;height:7px;border-radius:50%;background:#589388}.concept-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}.concept-tile{border-radius:17px;border:1px solid var(--border);background:var(--bg);padding:19px 20px;position:relative;color:var(--ink)}.mint{--bg:#edf8f2;--border:#cfe8da;--ink:#236947}.rose{--bg:#fff1ee;--border:#f1d6ce;--ink:#a14736}.blue{--bg:#edf5ff;--border:#cfe0f5;--ink:#285f99}.violet{--bg:#f5f0ff;--border:#e2d7f4;--ink:#724c99}.tile-caption{font-size:12px;margin:0;opacity:.9}.concept-tile h3{font-size:30px;line-height:1.25;margin:12px 0 1px;font-weight:800;text-align:right}.tile-meaning{font-size:15px;font-weight:600;margin:0}.people{display:flex;gap:7px;margin:15px 0}.person{display:grid;place-items:center;width:27px;height:27px;border-radius:50%;border:1.5px solid currentColor;font-size:17px;font-weight:600}.person.filled{background:var(--ink);color:white;border-color:var(--ink)}.tile-example{font-size:14px;border-top:1px solid var(--border);padding-top:12px;margin:0;line-height:1.75;color:var(--ink)}.rule-note{background:#fff8e5;border-right:3px solid #d9ab35;color:#775d23;padding:14px 17px;border-radius:10px;font-size:14px;margin-top:18px}.rule-note .english-term{color:#79581c}.example{background:#f5f8fc;border:1px solid #e1e8f0;border-radius:16px;padding:18px 22px;margin-top:20px}.example-label{font-size:12px;color:#64768a;font-weight:700}.example p{font-size:17px;line-height:1.95;color:#314d71;margin:8px 0 0}.practice-card{border-top:4px solid #8cb2df}.practice-card .step-label{background:#edf4fe;color:#346592}.writing-card{border-top:4px solid #bca2de}.writing-card .step-label{background:#f4eefb;color:#735298}.choices{display:grid;gap:10px;margin:20px 0;counter-reset:answer}.choices button{direction:ltr;text-align:left;display:flex;align-items:center;gap:14px;font-size:16px;counter-increment:answer;padding:14px 16px}.choices button:before{content:counter(answer,upper-alpha);display:grid;place-items:center;border-radius:8px;background:#f0f3f7;width:28px;height:28px;flex-shrink:0;font-size:12px;color:#596d83;font-weight:700}.choices button.correct{background:#e8f6ed;border-color:#74a98a;color:#235d3c}.choices button.wrong{background:#fff0ed;border-color:#d88f7b;color:#a34f3a}.correct:before{background:#cce8d6!important}.wrong:before{background:#f5d9d1!important}.muted{color:#697789;font-size:13px}.actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:16px}textarea{width:100%;min-height:170px;border:1px solid #d8dfea;border-radius:14px;padding:18px;direction:ltr;background:#fbfcfe;line-height:1.8;font-size:16px}.feedback{min-height:30px;font-size:15px}progress{display:block;width:100%;height:6px;appearance:none;border:0;background:#ecf0f5;border-radius:10px;overflow:hidden;accent-color:#6399cb}progress::-webkit-progress-bar{background:#ecf0f5}progress::-webkit-progress-value{background:#6399cb;border-radius:10px}progress::-moz-progress-bar{background:#6399cb}#counter{margin:8px 0}#question{font-size:20px;line-height:1.7;margin:24px 0 16px;font-weight:650;color:#253f61}#task{font-size:16px;color:#546074;background:#f7f3fc;padding:16px;border-radius:12px;margin-bottom:20px}label{display:block;font-size:14px;margin:9px 0}input[type=checkbox]{accent-color:#805ca5}footer{font-size:12px;color:#6d7a86}.hidden{display:none}details{margin:16px 0}summary{cursor:pointer;font-size:14px;font-weight:600}h2 .english-term{color:inherit}nav .english-term{overflow-wrap:anywhere}
@media(max-width:850px){.layout{grid-template-columns:1fr}nav{position:static;grid-template-columns:repeat(3,minmax(0,1fr));gap:6px}nav button{background:#fff;border-color:#e1e7ec;align-items:flex-start;font-size:12px;padding:10px;gap:7px}.lesson-number{width:24px;height:24px;font-size:10px;border-radius:7px}.lesson-name .english-term{font-size:11px}header,main,footer{padding:20px}.hero{padding:24px}.card{padding:23px}}
@media(max-width:480px){body{font-size:16px}header,main,footer{padding:16px}header{font-size:12px}header a:first-child{font-size:21px}.hero{padding:20px;border-radius:20px}.hero p{font-size:14px}.eyebrow{font-size:11px}h1{font-size:28px}h2{font-size:22px;line-height:1.7}.layout{margin-top:18px;gap:18px}nav{grid-template-columns:repeat(2,minmax(0,1fr))}.card{padding:19px;border-radius:19px}.concept-grid{gap:10px}.concept-tile{padding:14px 12px;border-radius:13px}.concept-tile h3{font-size:26px}.tile-caption{font-size:11px}.tile-example{font-size:13px;line-height:1.6}.example{padding:15px}.example p{font-size:15px}.rule-list li{font-size:15px;padding-right:32px}.rule-list li:before{right:13px}.rule-note{font-size:13px}.step-label,.page-label{font-size:11px}#question{font-size:18px}.choices button{font-size:15px;padding:12px;gap:10px}}
@media(prefers-reduced-motion:no-preference){button{transition:background .15s,border-color .15s}}

.unit-video{margin:24px 0 0;border-color:#c9ded5;background:linear-gradient(110deg,#edf6f0,#fff)}.video-intro h2{margin:8px 0;font-size:25px}.video-intro p{color:#5d7168;font-size:15px}.video-intro button{margin-top:10px}#video-panel{margin-top:24px}#video-panel[hidden]{display:none}#unit-player{display:block;max-height:76vh;width:100%;max-width:440px;aspect-ratio:9/16;object-fit:contain;background:#143c37;margin:0 auto;border-radius:16px}#video-chapters{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px;margin-top:14px}#video-chapters button{font-size:13px}.video-links{display:flex;gap:20px;flex-wrap:wrap;font-size:14px}@media(max-width:480px){#video-chapters{grid-template-columns:1fr}.video-intro h2{font-size:22px}}