:root{--paper:#f7f2e8;--card:#fffdf8;--ink:#17243a;--muted:#6f756f;--line:#ded9cf;--coral:#f26b4d;--coral-soft:#fff0ea;--sage:#789289;--success:#31735c;--danger:#b4493f;--font-sans:-apple-system, BlinkMacSystemFont, "Segoe UI", Arial, "PingFang SC", "Microsoft YaHei", sans-serif}*{box-sizing:border-box}html{background:var(--paper)}body{background:radial-gradient(circle at 100% 0%, #f26b4d1f, transparent 28rem), var(--paper);color:var(--ink);font-family:var(--font-sans);-webkit-font-smoothing:antialiased;margin:0}button,input,textarea{font:inherit}button{-webkit-tap-highlight-color:transparent}.quiz-shell{width:min(100%,720px);min-height:100vh;margin:0 auto;padding:0 16px 104px}.topbar{z-index:10;isolation:isolate;padding:17px 2px 13px;position:sticky;top:0}.topbar:before{inset-block:0;z-index:-1;background:color-mix(in srgb, var(--paper) 91%, transparent);-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);content:"";border-bottom:1px solid #17243a14;width:100vw;position:absolute;left:50%;transform:translate(-50%)}.topline{justify-content:space-between;align-items:center;gap:14px;display:flex}.section-label{white-space:nowrap;text-overflow:ellipsis;min-width:0;font-size:14px;font-weight:700;overflow:hidden}.counter{color:var(--muted);flex:none;font-size:13px}.counter b{color:var(--ink);font-size:17px}.progress-track{background:#dedbd3;border-radius:99px;height:4px;margin-top:11px;overflow:hidden}.progress-track span{border-radius:inherit;background:var(--coral);height:100%;transition:width .25s;display:block}.question-card{background:#fffdf8f0;border:1px solid #17243a17;border-radius:22px;margin-top:9px;padding:18px;box-shadow:0 18px 50px #252b3014}.material-wrap{border-bottom:1px solid var(--line);margin:-2px 0 20px}.material-toggle{width:100%;color:var(--sage);cursor:pointer;background:0 0;border:0;justify-content:space-between;align-items:center;padding:7px 0 14px;font-size:14px;font-weight:700;display:flex}.material-toggle span:last-child{font-size:21px;font-weight:400}.material{color:#3d4652;background:#f3efe7;border-radius:13px;max-height:52vh;margin:0 -4px 16px;padding:14px;overflow:auto}.material h2{color:var(--ink);font-family:var(--font-sans);margin:0 0 12px;font-size:18px;line-height:1.35}.material p{font-family:var(--font-sans);margin:0 0 12px;font-size:15px;line-height:1.68}.material p:last-child{margin-bottom:0}.material .study-hint{color:var(--sage);border-bottom:1px solid #ddd7cc;margin:-2px 0 13px;padding-bottom:10px;font-family:Arial,PingFang SC,sans-serif;font-size:12px;font-weight:700}.interactive-paragraph{position:relative}.paragraph-index{color:#52665f;vertical-align:2px;background:#e4e9e4;border-radius:7px;place-items:center;min-width:21px;height:21px;margin-right:6px;font-family:Arial,sans-serif;font-size:11px;font-weight:800;display:inline-grid}.interactive-sentence{cursor:pointer;-webkit-tap-highlight-color:transparent;-webkit-user-select:none;user-select:none;background:0 0;border-radius:5px}.interactive-sentence:active{background:0 0}.interactive-word{color:inherit;font-family:inherit;font-size:inherit;line-height:inherit;cursor:pointer;background:0 0;border:0;margin:0;padding:1px 0;display:inline}.question-heading{grid-template-columns:40px 1fr;align-items:start;gap:12px;display:grid}.question-number{background:var(--coral);color:#fff;border-radius:12px;place-items:center;width:38px;height:38px;font-size:16px;font-weight:800;display:grid;box-shadow:0 7px 18px #f26b4d3d}.question-kicker{color:var(--muted);letter-spacing:.06em;margin:1px 0 6px;font-size:12px;font-weight:700}.question-heading h1{color:var(--ink);font-family:var(--font-sans);overflow-wrap:anywhere;margin:0;font-size:clamp(19px,5vw,25px);line-height:1.48}.translation{color:var(--muted);margin:9px 0 0;font-size:14px;line-height:1.55}.options{justify-items:start;gap:9px;margin:22px 0 18px 50px;display:grid}.option{border:1px solid var(--line);width:auto;max-width:min(100%,520px);color:var(--ink);text-align:left;cursor:pointer;background:#fff;border-radius:13px;grid-template-columns:30px minmax(0,1fr);align-items:center;gap:10px;padding:10px 14px 10px 10px;line-height:1.42;transition:border-color .15s,background .15s,transform .15s;display:grid}.option:active{transform:scale(.99)}.option.selected{border-color:var(--coral);background:var(--coral-soft)}.option.correct{border-color:var(--success);background:#eaf5ef}.option.wrong{border-color:var(--danger);background:#fff0ee}.option-key{color:#52635d;background:#eef0ec;border-radius:9px;place-items:center;width:28px;height:28px;font-weight:800;display:grid}.option.selected .option-key{background:var(--coral);color:#fff}.option.correct .option-key{background:var(--success);color:#fff}.option.wrong .option-key{background:var(--danger);color:#fff}.options.word-bank{flex-wrap:wrap;align-items:flex-start;max-width:520px;display:flex}.word-bank .option{flex:none;grid-template-columns:27px auto;padding:7px 11px 7px 7px}.word-bank .option-key{border-radius:8px;width:25px;height:25px;font-size:13px}.text-answer{color:var(--muted);gap:8px;margin:22px 0 18px 50px;font-size:13px;font-weight:700;display:grid}.text-answer input,.text-answer textarea{border:1px solid var(--line);width:min(100%,520px);color:var(--ink);background:#fff;border-radius:13px;outline:none;font-weight:400}.text-answer input{height:46px;padding:0 13px}.text-answer textarea{resize:vertical;min-height:150px;padding:12px 13px;line-height:1.6}.text-answer input:focus,.text-answer textarea:focus{border-color:var(--coral);box-shadow:0 0 0 3px #f26b4d1f}.reveal-button{border:1px solid var(--ink);width:auto;color:var(--ink);cursor:pointer;background:0 0;border-radius:11px;margin:4px 0 0 50px;padding:10px 14px;font-size:14px;font-weight:700}.reveal-button.active{background:#e9ece8;border-color:#0000}.answer-panel{border-left:4px solid var(--coral);background:#f5f0e7;border-radius:0 14px 14px 0;margin:18px 0 0 50px;padding:16px}.panel-label{color:var(--muted);letter-spacing:.08em;margin:0 0 7px;font-size:12px;font-weight:800}.answer-line{align-items:center;gap:9px;margin:0;font-size:17px;display:flex}.answer-badge{background:var(--success);color:#fff;border-radius:9px;place-items:center;min-width:29px;height:29px;padding:0 8px;font-weight:800;display:grid}.completed-sentence{font-family:var(--font-sans);margin:12px 0 0;line-height:1.6}.explanation{border-top:1px solid #d8d3ca;margin-top:16px;padding-top:14px}.explanation>p:last-child{margin:0;line-height:1.7}.reference-answer h3{font-family:var(--font-sans);margin:0 0 12px;font-size:19px}.reference-answer p{font-family:var(--font-sans);margin:0 0 10px;line-height:1.65}.bottom-nav{z-index:20;padding:12px 16px calc(12px + env(safe-area-inset-bottom));-webkit-backdrop-filter:blur(14px);backdrop-filter:blur(14px);background:#fffdf8ed;border-top:1px solid #17243a1a;grid-template-columns:minmax(88px,150px) minmax(150px,330px);justify-content:center;gap:10px;display:grid;position:fixed;bottom:0;left:0;right:0}.bottom-nav button{border:1px solid var(--line);height:48px;color:var(--ink);cursor:pointer;background:#fff;border-radius:14px;font-weight:800}.bottom-nav .next-button{border-color:var(--ink);background:var(--ink);color:#fff}.bottom-nav button:disabled{cursor:default;opacity:.4}.learning-overlay{z-index:50;-webkit-backdrop-filter:blur(3px);backdrop-filter:blur(3px);background:#111a2861;justify-content:center;align-items:flex-end;padding:18px;animation:.16s ease-out overlay-in;display:flex;position:fixed;inset:0}.learning-popup{width:min(100%,560px);padding:10px 18px calc(20px + env(safe-area-inset-bottom));background:var(--card);border:1px solid #17243a1a;border-radius:22px;animation:.2s ease-out sheet-in;box-shadow:0 24px 70px #111a2840}.popup-handle{background:#d8d4cb;border-radius:99px;width:38px;height:4px;margin:0 auto 14px}.popup-heading{justify-content:space-between;align-items:flex-start;gap:14px;display:flex}.popup-heading p{color:var(--coral);margin:0 0 4px;font-size:12px;font-weight:800}.popup-heading h2{font-family:var(--font-sans);overflow-wrap:anywhere;margin:0;font-size:22px;line-height:1.35}.popup-heading button{color:var(--muted);cursor:pointer;background:#ece9e1;border:0;border-radius:9px;flex:none;padding:7px 10px;font-size:13px;font-weight:700}.popup-meaning{background:var(--coral-soft);color:var(--ink);border-radius:13px;margin:18px 0 0;padding:14px;font-size:17px;font-weight:700;line-height:1.65}@keyframes overlay-in{0%{opacity:0}}@keyframes sheet-in{0%{opacity:0;transform:translateY(24px)}}.status-page{min-height:100vh;color:var(--muted);place-content:center;justify-items:center;gap:12px;display:grid}.loader{border:3px solid #ddd7cb;border-top-color:var(--coral);border-radius:50%;width:28px;height:28px;animation:.8s linear infinite spin}@keyframes spin{to{transform:rotate(360deg)}}@media (width<=520px){.quiz-shell{padding-left:12px;padding-right:12px}.question-card{border-radius:19px;padding:16px 14px 18px}.question-heading{grid-template-columns:34px 1fr;gap:10px}.question-number{border-radius:10px;width:34px;height:34px;font-size:14px}.options,.text-answer,.reveal-button,.answer-panel{margin-left:44px}.option{padding:9px 11px 9px 9px;font-size:15px}.answer-panel{padding:14px}.learning-overlay{padding:10px}.learning-popup{border-radius:20px}}@media (width<=370px){.options,.text-answer,.reveal-button,.answer-panel{margin-left:0}.question-heading{margin-bottom:18px}}@media (prefers-reduced-motion:reduce){*,:before,:after{scroll-behavior:auto!important;transition:none!important}}