/* Reusable source-tracked lesson interface. Fonts load from official Google Fonts with robust local fallbacks. */
.l31-wrap{
  --l31-ink:var(--ink);--l31-muted:var(--ink3);--l31-line:var(--line);--l31-paper:var(--paper);
  --l31-cream:var(--paper2);--l31-green:var(--tai);--l31-green-dark:var(--tai);--l31-rust:var(--jusha);
  --l31-gold:var(--jin);--l31-shadow:var(--sh);
  max-width:1180px;margin:0 auto;padding:0 26px 64px;color:var(--l31-ink);
  font-family:var(--f-ui);font-size:inherit;line-height:1.7;
}
.l31-wrap *{box-sizing:border-box;min-width:0}
.l31-wrap .zh{font-family:var(--f-zh)}
.l31-wrap :where(button,input,textarea,select){font-family:var(--f-ui)}
.l31-wrap .l31-pinyin,.l31-wrap .l31-py-inline{font-family:var(--f-ui)}
.l31-wrap .l31-zh-text,.l31-wrap .l31-reading-title,.l31-wrap .l31-reading-passage .zh{font-family:var(--f-zh)}
.l31-wrap a{color:var(--l31-green-dark)}
.l31-wrap a:focus-visible,.l31-wrap button:focus-visible,.l31-wrap input:focus-visible,.l31-wrap textarea:focus-visible,.l31-wrap select:focus-visible,.l31-wrap summary:focus-visible{outline:3px solid var(--dian);outline-offset:2px}
.l31-wrap p{line-height:1.75}
.l31-hero{position:relative;overflow:hidden;margin:16px 0 14px;padding:clamp(22px,4vw,42px);border:1px solid #d6e2da;border-radius:24px;background:radial-gradient(circle at 90% 15%,rgba(255,255,255,.65),transparent 28%),linear-gradient(135deg,#e5efe9,#f5f0e6 75%);box-shadow:var(--l31-shadow)}
.l31-hero-kicker,.l31-eyebrow{font-size:11px;font-weight:800;letter-spacing:.12em;text-transform:uppercase;color:var(--l31-green);margin-bottom:7px}
.l31-title{margin:0;font-size:clamp(32px,5vw,54px);line-height:1.18;letter-spacing:.02em;color:#213b35}
.l31-hero-sub{max-width:750px;margin:12px 0 22px;color:#52625c;font-size:15px}
.l31-hero-actions{display:flex;align-items:center;gap:10px;flex-wrap:wrap}
.l31-progress{flex:1 1 300px;max-width:420px;margin-left:auto;padding:12px 15px;border:1px solid rgba(49,95,85,.16);border-radius:14px;background:rgba(255,255,255,.7)}
.l31-progress-head{display:flex;justify-content:space-between;gap:10px;font-size:12px}.l31-progress-head span{font-weight:800;color:var(--l31-green)}
.l31-progress-track{height:7px;margin:8px 0 5px;border-radius:99px;background:#dfe8e2;overflow:hidden}.l31-progress-track i{display:block;height:100%;border-radius:inherit;background:linear-gradient(90deg,#4f8373,#b98738)}
.l31-progress small{color:var(--l31-muted);font-size:10px}
.l31-tabs{display:flex;gap:6px;overflow-x:auto;overscroll-behavior-inline:contain;padding:5px 2px 9px;margin:12px 0 14px;scrollbar-width:thin}
.l31-tab{display:inline-flex;align-items:center;justify-content:center;flex:none;min-height:42px;padding:9px 15px;border:1px solid var(--l31-line);border-radius:999px;background:#fff;color:#4f5d58!important;text-decoration:none;font-size:13px;font-weight:700;white-space:nowrap;transition:background .15s,border-color .15s,color .15s}
.l31-tab:hover{border-color:#9bb8a9;background:#f1f7f2}.l31-tab.is-active{border-color:var(--l31-green);background:var(--l31-green);color:white!important}
.l31-panel{min-height:240px;padding:clamp(16px,3vw,32px);border:1px solid var(--l31-line);border-radius:22px;background:var(--l31-paper);box-shadow:var(--l31-shadow)}
.l31-page{max-width:100%;overflow-wrap:anywhere}.l31-page-heading{display:flex;align-items:flex-start;justify-content:space-between;gap:20px;margin:0 0 18px}.l31-page-heading h2{margin:0;font-size:clamp(24px,3.2vw,34px);line-height:1.2;color:#263e37}.l31-page-heading p{margin:7px 0 0;color:var(--l31-muted);font-size:14px}
.l31-layer{display:inline-flex;align-items:center;max-width:100%;padding:4px 9px;border:1px solid #dbe5dd;border-radius:999px;background:#edf4ee;color:#3b6556;font-size:10px;font-weight:800;line-height:1.35;white-space:normal;overflow-wrap:anywhere}
.l31-layer.l31-source{border-color:#e6d6bf;background:#faf1e3;color:#795d36}.l31-layer.l31-support{border-color:#d9d7ef;background:#f2f1fb;color:#585486}
.l31-toggles{display:flex;align-items:center;gap:8px;flex-wrap:wrap;padding:11px 13px;margin:12px 0 17px;border:1px solid var(--l31-line);border-radius:14px;background:#f8faf7}
.l31-toggles button{min-height:40px;padding:8px 13px;border:1px solid #cbd8cf;border-radius:999px;background:#fff;color:#35574b;font-weight:750;cursor:pointer}.l31-toggles button.on{background:#315f55;border-color:#315f55;color:#fff}.l31-toggle-hint{color:var(--l31-muted);font-size:11px}
.l31-btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;min-height:42px;padding:9px 14px;border:1px solid #cad8d0;border-radius:11px;background:#fff;color:#2c584c!important;text-decoration:none;font-size:13px;font-weight:750;line-height:1.35;cursor:pointer;transition:transform .15s,background .15s,border-color .15s}
.l31-btn:hover{background:#f2f7f3;border-color:#8eaa9c;transform:translateY(-1px)}.l31-btn:disabled{opacity:.55;cursor:not-allowed;transform:none}
.l31-btn-primary{border-color:var(--l31-green);background:var(--l31-green);color:#fff!important}.l31-btn-primary:hover{background:var(--l31-green-dark);border-color:var(--l31-green-dark)}
.l31-btn-soft{background:#f5f7f3}.l31-btn-quiet{background:rgba(255,255,255,.65)}
.l31-card{padding:18px;border:1px solid var(--l31-line);border-radius:16px;background:#fff;box-shadow:0 4px 15px rgba(30,53,45,.035)}
.l31-card h3{margin:0 0 9px;font-size:18px}.l31-card p{margin:8px 0}.l31-card-feature{display:flex;align-items:center;gap:22px;background:linear-gradient(145deg,#f2f8f3,#fff)}.l31-card-feature h3{font-size:clamp(25px,4vw,38px);margin:0 0 8px}.l31-card-mark{display:grid;place-items:center;flex:none;width:72px;height:72px;border-radius:22px;background:#315f55;color:white;font-size:28px;font-weight:850;box-shadow:0 8px 20px rgba(49,95,85,.18)}
.l31-card-label,.l31-card-label>.l31-layer{margin-bottom:8px}
.l31-learning-box{padding:14px 16px;margin:13px 0;border:1px solid #e2e0f0;border-radius:14px;background:#f7f6fd}.l31-learning-box>b{color:#514e7a}.l31-learning-box p{margin:7px 0}.l31-learning-box ul{margin:8px 0;padding-left:20px}.l31-learning-box li{margin:5px 0}.l31-learning-box small{color:var(--l31-muted);font-size:11px}
.l31-existing-features{margin:14px 0;background:#f6faf7}.l31-existing-features>div{display:flex;flex-wrap:wrap;gap:8px}.l31-existing-features small{display:block;margin-top:9px;color:var(--l31-muted)}
.l31-section-title{margin:26px 0 12px;font-size:20px}.l31-grid-cards{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:11px}.l31-step-card{position:relative;display:flex;flex-direction:column;gap:7px;min-height:150px;padding:16px;border:1px solid var(--l31-line);border-radius:15px;background:#fff;color:var(--l31-ink)!important;text-decoration:none;transition:transform .15s,box-shadow .15s}.l31-step-card:hover{transform:translateY(-2px);box-shadow:var(--l31-shadow)}.l31-step-card>b{font-size:15px}.l31-step-card>span:not(.l31-step-num){font-size:12px;color:var(--l31-muted);line-height:1.5}.l31-step-card>i{position:absolute;right:14px;bottom:10px;color:var(--l31-rust);font-style:normal}.l31-step-num{display:inline-grid;place-items:center;width:31px;height:28px;border-radius:9px;background:#edf3ee;color:#315f55;font-size:11px;font-weight:850}
.l31-inline-note{padding:12px 14px;margin:14px 0;border:1px solid #dfe8e3;border-radius:12px;background:#f5f8f5;color:#51625a;font-size:12px;line-height:1.65}.l31-inline-note b{color:#334f44}.l31-page-foot{display:flex;flex-wrap:wrap;gap:8px;margin-top:18px}.l31-footer{border-top:1px solid var(--l31-line);padding:16px 0;color:#73766d;font-size:11px;line-height:1.7}
.l31-gate-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin:14px 0 18px}.l31-gate{display:flex;flex-direction:column;align-items:flex-start;gap:8px;min-height:128px;padding:16px;border:1px solid var(--l31-line);border-radius:14px;background:#fff;color:var(--l31-ink);text-align:left;cursor:pointer}.l31-gate:hover{border-color:var(--l31-green);background:var(--l31-cream)}.l31-gate.on{border-color:var(--l31-green);background:var(--l31-cream)}.l31-gate-number{color:var(--l31-muted);font-size:11px;font-weight:750}.l31-gate b{font-size:17px}.l31-gate>span:last-child{color:var(--l31-muted);font-size:12px;line-height:1.55}.l31-gate-content{min-height:68px;padding:12px 0}.l31-source-disclosure{margin:14px 0;border-top:1px solid var(--l31-line);padding:14px 0}.l31-source-disclosure>summary{cursor:pointer;font-weight:750;color:var(--l31-green-dark)}
.l31-reading-tools{display:flex;gap:8px;flex-wrap:wrap;margin:12px 0}.l31-pill{display:inline-flex;padding:7px 10px;border:1px solid var(--l31-line);border-radius:999px;background:#f8faf7;color:#5c6762;font-size:11px}.l31-reading-title{margin:18px 0 13px;font-size:28px;color:#273f38}.l31-reading{display:grid;gap:14px}.l31-paragraph{padding:17px 19px;border:1px solid #e3e7e1;border-radius:16px;background:#fff;box-shadow:0 4px 12px rgba(40,52,45,.03)}.l31-paragraph-head{display:flex;justify-content:space-between;gap:8px;color:#738079;font-size:11px;font-weight:750}.l31-audio{display:block;width:100%;height:42px;margin:10px 0 4px}.l31-audio-actions{display:flex;align-items:center;gap:8px;flex-wrap:wrap;min-height:26px}.l31-audio-status,.l31-inline-status{color:#637068;font-size:12px}.l31-zh-text{margin:10px 0 0;font-size:20px;line-height:2.05;letter-spacing:.02em;white-space:pre-wrap;overflow-wrap:anywhere}.l31-pinyin{margin:8px 0;color:#536b87;font-family:ui-sans-serif,system-ui,sans-serif;font-size:14px;line-height:1.7;overflow-wrap:anywhere}.l31-translation{margin:8px 0;padding:8px 11px;border-left:3px solid #7b8fbb;background:#f3f5fb;color:#48577b;line-height:1.7;overflow-wrap:anywhere}.l31-missing,.l31-muted{color:var(--l31-muted);font-size:12px}.l31-reading-citation{margin:12px 3px;color:#68736f;font-size:12px;text-align:right}
.l31-paragraph-actions{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin-top:9px}
.l31-speak-button{min-height:38px;padding:7px 11px;border:1px solid #b9cfc1;border-radius:10px;background:#f4faf5;color:#315f55;font-weight:750;cursor:pointer}
.l31-speak-button:hover{background:#e9f3ec;border-color:#88a995}
.l31-tts-status{color:var(--l31-muted);font-size:11px}
.l31-vocab-tip{position:relative;display:inline-block;vertical-align:baseline}
.l31-vocab-tip>summary{display:inline;list-style:none;cursor:pointer;border-bottom:1px dotted #668775;color:#244f42;text-underline-offset:3px}
.l31-vocab-tip>summary::-webkit-details-marker{display:none}
.l31-vocab-tip[open]>summary{border-bottom-style:solid;color:#1e4237}
.l31-vocab-pop{position:fixed;z-index:30;top:auto;left:auto;right:auto;width:min(320px,calc(100vw - 28px));max-height:min(62vh,390px);overflow:auto;padding:14px;border:1px solid #cddbd0;border-radius:13px;background:#fff;box-shadow:var(--sh2);font-family:var(--f-ui);font-size:13px;line-height:1.55;color:#343a35}

.l31-vocab-pop h4{margin:0 0 5px;color:#29473e;font-family:var(--f-zh);font-size:23px;line-height:1.3}
.l31-vocab-pop p{margin:5px 0;line-height:1.55}
.l31-vocab-pop .l31-vocab-pop-example{margin-top:9px;padding-top:8px;border-top:1px solid #e8eee9}
.l31-vocab-pop .zh{font-family:var(--f-zh);font-size:15px;line-height:1.7}
.l31-vocab-card-example{margin:8px 0;color:#4a5b50;font-size:12px;line-height:1.65}
.l31-vocab-card-example .zh{display:block;margin-top:3px;font-family:var(--f-zh);font-size:14px;line-height:1.75}
.l31-vocab-card .l31-speak-button{margin-top:7px}
.l31-vocab-body .l31-vocab-meta{justify-content:flex-start}

.l31-vocab-search,.l31-search{display:flex;align-items:center;gap:8px;margin:12px 0}.l31-vocab-search input,.l31-search input{width:100%;min-height:42px;padding:9px 12px;border:1px solid #cfd9d2;border-radius:11px;background:#fff;color:var(--l31-ink);font-size:15px}.l31-search-label{color:var(--l31-muted);font-size:12px}
.l31-vocab-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.l31-vocab-card{display:grid;grid-template-columns:minmax(130px,34%) minmax(0,1fr);min-height:190px;border:1px solid var(--l31-line);border-radius:16px;overflow:hidden;background:#fff}.l31-vocab-image,.l31-image-exception{display:flex;flex-direction:column;justify-content:center;align-items:center;min-height:190px;margin:0;padding:9px;background:#f0f4ef;text-align:center}.l31-vocab-image img{width:100%;height:145px;object-fit:cover;border-radius:9px}.l31-vocab-attribution{align-self:stretch;margin-top:6px;text-align:left;color:#61736a;font-size:11px;line-height:1.45}.l31-vocab-attribution summary{cursor:pointer;color:#536b5e;font-weight:700}.l31-vocab-attribution a{display:block;margin-top:4px;font-size:11px;overflow-wrap:anywhere}.l31-image-exception{padding:13px;background:#f8f4eb;color:#655b49}.l31-image-symbol{font-size:24px;color:#a4844e}.l31-image-exception b{font-size:12px}.l31-image-exception small{margin-top:6px;font-size:10px;line-height:1.45}.l31-vocab-body{padding:13px 14px}.l31-vocab-meta{display:flex;align-items:center;justify-content:space-between;gap:6px;color:#748078;font-size:10px}.l31-vocab-body h3{margin:5px 0;font-size:28px;line-height:1.2}.l31-pos{margin:4px 0;color:#69736e;font-size:11px}.l31-vocab-example{margin-top:9px;padding-top:8px;border-top:1px solid #edf0ec}.l31-vocab-example summary{color:#476457;font-size:11px;font-weight:700;cursor:pointer}.l31-vocab-example p{margin:7px 0;font-size:14px;line-height:1.8}.l31-word-audio{display:grid;grid-template-columns:1fr;gap:6px;margin:14px 0;padding:14px;border:1px solid var(--l31-line);border-radius:14px;background:#f8faf7}.l31-word-audio audio{width:100%}.l31-word-audio small{color:var(--l31-muted)}.l31-word-play{min-height:38px;margin-top:6px;padding:7px 10px;border:1px solid #b9cfc1;border-radius:10px;background:#f4faf5;color:#315f55;font-weight:750;cursor:pointer}
.l31-grammar-card{margin:12px 0;padding:17px;border:1px solid var(--l31-line);border-radius:16px;background:#fff}.l31-grammar-title{display:flex;align-items:center;gap:9px;flex-wrap:wrap;margin:0 0 8px}.l31-grammar-title .zh{font-size:22px}.l31-examples{display:grid;gap:8px;margin:10px 0}.l31-example{padding:10px 12px;border-left:3px solid #8b9d86;border-radius:7px;background:#f6f8f3}.l31-example .zh{font-size:16px;line-height:1.9}.l31-example-more{color:var(--l31-muted);font-size:11px}.l31-colloc-list{display:grid;gap:10px}.l31-colloc-card{display:grid;grid-template-columns:36px 1fr;gap:12px;padding:15px;border:1px solid var(--l31-line);border-radius:14px;background:#fff}.l31-colloc-card p{margin:4px 0;line-height:1.8}.l31-colloc-card .zh{font-size:17px}.l31-colloc-example{color:#526a5e}.l31-extension-card{margin:10px 0}.l31-extension-card p{font-size:17px;line-height:2}.l31-extension-list{padding-left:23px}.l31-extension-list li{margin:8px 0;line-height:1.9}.l31-context{margin:10px 0}.l31-learning-context{background:#f8f7fc}.l31-rubric{padding:14px;border:1px dashed #c7c6de;border-radius:12px;background:#f9f8fd;color:#5b587d;font-size:12px}
.l31-exercise-group{min-width:0;margin:14px 0;padding:16px;border:1px solid var(--l31-line);border-radius:15px;background:#fff}.l31-exercise-group legend{max-width:100%;padding:0 8px;color:#2e5146;font-size:15px;font-weight:800;overflow-wrap:anywhere}.l31-qrow{padding:9px 0;border-bottom:1px solid #edf0ec}.l31-qrow:last-of-type{border-bottom:0}.l31-qrow>p,.l31-qrow>label{display:block;margin:0;line-height:1.8;overflow-wrap:anywhere}.l31-qnum{display:inline-grid;place-items:center;min-width:27px;height:25px;margin-right:5px;padding:0 5px;border-radius:8px;background:#edf3ee;color:#315f55;font-family:system-ui,sans-serif;font-size:11px;font-weight:850;vertical-align:middle}.l31-word-bank{padding:9px 11px;margin:5px 0 10px;border-radius:10px;background:#f8f5ec;color:#625843;font-size:12px;line-height:1.8}.l31-inline-answer{display:inline-block;max-width:min(220px,45vw);min-width:110px;min-height:40px;padding:6px 9px;border:1px solid #aebfb3;border-radius:8px;background:#fff;font-size:16px}.l31-options{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:7px;margin:9px 0 3px}.l31-options label{display:flex;align-items:flex-start;gap:8px;min-height:42px;padding:9px 10px;border:1px solid #e0e6e0;border-radius:10px;background:#fcfdfb;cursor:pointer;line-height:1.55}.l31-options label:has(input:checked){border-color:#709581;background:#eff7f0}.l31-options input{flex:none;margin-top:4px;accent-color:#315f55}.l31-match-heading{margin:12px 0 4px;color:#65716b;font-size:12px}.l31-match-row{display:grid;grid-template-columns:minmax(120px,1fr) 20px minmax(150px,1.2fr);align-items:center;gap:9px;padding:7px 0;border-bottom:1px solid #edf0ec}.l31-match-row select{width:100%;min-height:40px;padding:7px 9px;border:1px solid #cbd7cf;border-radius:8px;background:#fff}.l31-result{margin-top:12px;padding:11px;border:1px solid #dce6df;border-radius:11px;background:#f6faf6}.l31-result ul{padding-left:21px}.l31-result li{margin:6px 0;line-height:1.65}.l31-result .is-correct{color:#286242}.l31-result .is-wrong{color:#8e493b}.l31-result small{display:block;margin-top:8px;color:var(--l31-muted);font-size:10px}.l31-reading-passage{margin:14px 0;padding:16px 18px;border-left:3px solid var(--l31-rust);border-radius:10px;background:#fffefa}.l31-reading-passage .zh{margin:0;white-space:pre-wrap;overflow-wrap:anywhere;line-height:2;font-size:17px}.l31-workbook{margin:22px 0;padding:clamp(14px,2.5vw,22px);border:1px solid var(--l31-line);border-radius:18px;background:#fbfaf6}.l31-workbook>h3{margin:0 0 8px;font-size:20px}.l31-audio-caution{margin:12px 0;padding:14px;border-color:#d4a163;background:#fff8ea}.l31-audio-source-links{display:flex;flex-wrap:wrap;gap:8px;margin:12px 0 6px}.l31-audio-source-links .l31-btn{min-height:42px}.l31-workbook textarea[data-kind="rebuild"]{width:100%;max-width:100%;min-height:54px;margin-top:7px;resize:vertical}.l31-workbook .l31-qrow,.l31-workbook .l31-options{min-width:0}

.l31-item-feedback{padding:12px;margin:10px 0 4px;border:1px solid var(--line);border-radius:var(--r-s);background:var(--paper2);font-size:14px;line-height:1.65}
.l31-item-feedback p{margin:6px 0}.l31-feedback-state.is-correct{color:var(--tai)}.l31-feedback-state.is-wrong{color:var(--jusha)}
.l31-feedback-answer{font-size:16px}.l31-feedback-vocab{margin-top:8px}.l31-feedback-options{margin:6px 0;padding-left:22px}.l31-feedback-options li{margin:5px 0}.l31-feedback-meta,.l31-feedback-limit{display:block;color:var(--ink3);font-size:12px}.l31-feedback-limit{margin-top:8px}
.l31-workbook-audio-list{display:grid;gap:10px}.l31-workbook-audio{display:grid;grid-template-columns:minmax(0,1fr);gap:6px;padding:12px;border:1px solid var(--line);border-radius:var(--r-s);background:var(--paper)}.l31-workbook-audio span{display:block;color:var(--ink3);font-size:13px}.l31-workbook-audio a{width:max-content;max-width:100%;overflow-wrap:anywhere}
.l31-workbook-audio .l31-audio{margin:4px 0}

.l31-answer-area{display:block;width:100%;max-width:100%;min-height:92px;margin:8px 0;padding:11px 12px;border:1px solid #cbd7cf;border-radius:10px;background:#fff;color:var(--l31-ink);font:inherit;font-size:16px;line-height:1.7;resize:vertical}.l31-writing-card,.l31-retell-item{margin:12px 0;padding:16px;border:1px solid var(--l31-line);border-radius:15px;background:#fff}.l31-writing-title{display:flex;align-items:center;justify-content:space-between;gap:10px;flex-wrap:wrap}.l31-writing-title h3,.l31-retell-item h4{margin:0;font-size:17px}.l31-writing-prompt,.l31-retell-item>.zh{font-size:16px;line-height:1.9}.l31-writing-actions{display:flex;gap:8px;align-items:center;flex-wrap:wrap}.l31-ai-feedback{padding:12px;margin-top:10px;border:1px solid #dad9ef;border-radius:11px;background:#f8f7fd;color:#514e73}.l31-ai-feedback>div{margin-top:7px;white-space:pre-wrap;line-height:1.7}.l31-retell-item .zh{line-height:1.9;overflow-wrap:anywhere}
.l31-exercise-source,.l31-source-details{margin:12px 0;padding:12px 14px;border:1px solid var(--l31-line);border-radius:12px;background:#f8faf7}.l31-exercise-source summary,.l31-source-details summary{color:#405d51;font-weight:750;cursor:pointer}.l31-pre{max-width:100%;padding:12px;border-radius:9px;background:#f2f2ee;white-space:pre-wrap;overflow-wrap:anywhere;overflow-x:auto;font-size:13px;line-height:1.8}
.l31-pre.l31-source-text{font-family:var(--f-ui);font-size:14px;line-height:1.8}.l31-pre.l31-source-text .zh{font-family:var(--f-zh)}.l31-pre.zh{font-family:var(--f-zh)}.l31-source-exercises li{margin:6px 0;line-height:1.9}.l31-page-foot{display:flex;flex-wrap:wrap;gap:8px;margin-top:18px}.l31-footer{border-top:1px solid var(--l31-line);padding:16px 0;color:#73766d;font-size:11px;line-height:1.7}
@media(max-width:900px){.l31-grid-cards{grid-template-columns:repeat(2,minmax(0,1fr))}.l31-wrap{padding:0 20px 54px}.l31-vocab-grid{grid-template-columns:1fr}}
@media(max-width:650px){
  .l31-wrap{padding:0 13px 42px}
  .l31-hero{padding:20px 16px;border-radius:16px}
  .l31-hero-actions{align-items:stretch}
  .l31-hero-actions>.l31-btn{flex:1}
  .l31-progress{margin-left:0;flex-basis:100%;max-width:none}
  .l31-tabs{margin:12px -2px 10px;gap:3px}
  .l31-tab{padding:9px 10px;font-size:12px}
  .l31-page-heading{display:block}
  .l31-page-heading>.l31-layer{margin-top:8px}
  .l31-page .l31-layer{max-width:100%;white-space:normal;overflow-wrap:anywhere}
  .l31-gate-grid{grid-template-columns:1fr}
  .l31-grid-cards{grid-template-columns:1fr 1fr;gap:8px}
  .l31-step-card{min-height:145px;padding:11px;font-size:13px}
  .l31-vocab-grid{grid-template-columns:1fr}
  .l31-vocab-card{grid-template-columns:minmax(100px,34%) minmax(0,1fr);min-height:155px}
  .l31-vocab-image,.l31-image-exception{min-height:150px}
  .l31-vocab-image img{height:125px}
  .l31-vocab-body{padding:10px}
  .l31-vocab-body h3{font-size:25px}
  .l31-paragraph{padding:13px}
  .l31-zh-text{font-size:18px;line-height:2}
  .l31-match-row{grid-template-columns:minmax(70px,1fr) 18px minmax(110px,1.2fr);gap:5px;font-size:13px}
  .l31-match-row select{padding:8px 5px;font-size:12px}
  .l31-card-feature{align-items:flex-start;gap:13px}
  .l31-options{grid-template-columns:1fr}
  .l31-reading-passage{padding:12px}
  .l31-reading-passage .zh{font-size:16px;line-height:1.9}
  .l31-audio-source-links{display:grid;grid-template-columns:1fr}
  .l31-audio-source-links .l31-btn{width:100%;justify-content:center}
  .l31-workbook{padding:12px}
}
@media(max-width:380px){
  .l31-grid-cards{grid-template-columns:1fr}
  .l31-step-card{min-height:105px}
  .l31-vocab-card{grid-template-columns:96px minmax(0,1fr)}
  .l31-vocab-image img{height:115px}
  .l31-image-exception{padding:8px}
  .l31-vocab-meta .l31-layer{font-size:8px;padding:3px 5px}
}
@media(prefers-reduced-motion:reduce){.l31-btn,.l31-step-card{transition:none}.l31-step-card:hover{transform:none}}