.lesson-main{max-width:1170px}.lesson-heading{display:flex;justify-content:space-between;align-items:center;gap:24px;margin-bottom:26px}.lesson-heading h1{font-size:36px;letter-spacing:-1px}.lesson-heading p{line-height:1.7;margin:0;color:#536581}.lesson-heading p span{font-size:14px}.practice-link{font-size:14px;color:#596b86;text-decoration:none;max-width:180px;line-height:1.7}.practice-link:hover{text-decoration:underline}.lesson-nav{display:grid;grid-template-columns:repeat(5,1fr);gap:8px;margin-bottom:20px}.lesson-nav button{border:1px solid #dbe1ed;border-radius:10px;padding:13px 10px;background:#fff;text-align:left;color:#596b86;font-size:14px;line-height:1.5}.lesson-nav button[aria-current=step]{background:#213ee6;color:white;border-color:#213ee6}.lesson-nav button span{display:block;font-size:12px;opacity:.8;margin-bottom:4px}.lesson-panel{background:#fff;border:1px solid var(--line);border-radius:18px;padding:30px 38px}.lesson-kicker{display:flex;justify-content:space-between;font-size:12px;letter-spacing:1px;font-weight:700;color:#657696;margin-bottom:20px}.lesson-panel h2{font:800 29px/1.3 Manrope,Arial,sans-serif;margin:0 0 12px;letter-spacing:-.5px}.lesson-panel h3{font-size:18px;margin:0 0 12px}.lesson-panel p{line-height:1.7;margin:10px 0 16px}.zh{display:block;color:#66758e;font-size:14px;margin-top:5px}.lesson-columns{display:grid;grid-template-columns:1.15fr 1fr;gap:28px;margin-top:24px;align-items:start}.diagram{background:#f5f7fc;border:1px solid #e4e9f4;padding:22px;border-radius:12px}.diagram .math{font-size:25px;line-height:1.6}.bar-row{display:grid;grid-template-columns:22px 1fr 38px;gap:9px;align-items:center;margin:18px 0}.bar-label{font:italic 23px Georgia,serif}.bar-track{height:30px;background:#e3e8f2;border-radius:4px;overflow:hidden}.bar-fill{width:var(--width);height:100%;background:var(--color);background-image:linear-gradient(90deg,transparent calc(100% - 2px),#ffffff88 0);background-size:var(--unit) 100%;transition:width .3s}.bar-number{font-size:17px;font-weight:700}.legend{font-size:13px;color:#63708a}.button-group{display:flex;flex-wrap:wrap;gap:9px;margin:16px 0}.secondary,.choice{border:1px solid #ccd5e5;border-radius:8px;background:white;padding:12px 17px;color:#30415f;font-weight:600;font-size:15px}.choice[aria-pressed=true]{background:#eaf0ff;border-color:#213ee6;color:#213ee6}.choice:hover,.secondary:hover{border-color:#213ee6}.lesson-callout{background:#eef2ff;border-left:3px solid #213ee6;padding:16px 19px;line-height:1.7;border-radius:0 8px 8px 0;margin:20px 0}.lesson-callout .math{font-size:24px}.lesson-feedback{line-height:1.7;padding:14px 17px;background:#fff3df;color:#75501e;border-radius:9px;margin:14px 0}.lesson-feedback:empty{display:none}.lesson-feedback.good{background:#e8f7f1;color:#22684f}.lesson-pagination{border-top:1px solid var(--line);padding-top:22px;margin-top:30px;display:flex;gap:16px;align-items:center;justify-content:space-between}.lesson-pagination span{font-size:13px;color:#68758f}.lesson-panel details{border:1px solid #dfe5f0;border-radius:9px;padding:14px 18px;margin:18px 0;line-height:1.8}.lesson-panel summary{cursor:pointer;font-size:15px;font-weight:600}.lesson-panel input[type=range]{width:100%;padding:0;height:32px;accent-color:#213ee6;border:0;outline-offset:4px}.k-values{display:flex;gap:16px;flex-wrap:wrap;font:24px Georgia,serif;margin:18px 0}.k-values span{padding:9px 14px;border-radius:8px;background:white;border:1px solid #dde4f0}.guided-form{display:flex;align-items:center;flex-wrap:wrap;gap:12px;margin-top:20px}.guided-form label{font:24px Georgia,serif;margin:0}.guided-form input{width:85px;flex:0 1 85px}.worked-line{font:23px/1.8 'Times New Roman',serif;padding:14px 0;border-bottom:1px solid #e5eaf3}.worked-line span.label{display:block;font:14px 'DM Sans',sans-serif;color:#68758f;margin-bottom:6px}.learning-check{display:flex;gap:10px;flex-wrap:wrap}.learning-check .choice{line-height:1.6;text-align:left}.recap-list{padding-left:22px;line-height:1.8}.recap-list li{margin:10px 0}.lesson-end{display:flex;gap:20px;align-items:center;flex-wrap:wrap;margin-top:25px}.lesson-end a{text-decoration:none}.lesson-end .secondary{display:inline-block}.lesson-panel button:disabled{opacity:.5}.lesson-panel .fraction{font-size:24px}.lesson-panel input{font-size:21px}.lesson-panel .note{font-size:14px;color:#64718b}.step-heading:focus{outline:none}@media(max-width:760px){.lesson-main{padding:24px 16px}.lesson-heading{display:block}.lesson-heading h1{font-size:30px}.practice-link{display:inline-block;margin-top:12px;max-width:none}.lesson-nav{grid-template-columns:repeat(5,minmax(0,1fr));gap:5px}.lesson-nav button{font-size:12px;padding:9px 5px;text-align:center;overflow-wrap:anywhere}.lesson-panel{padding:22px 18px}.lesson-panel h2{font-size:25px}.lesson-columns{grid-template-columns:1fr;gap:16px}.lesson-pagination{gap:8px;flex-wrap:wrap}.lesson-pagination span{display:none}.diagram{padding:17px}.guided-form .primary{width:100%}.lesson-heading .eyebrow{font-size:12px}.learning-check{flex-direction:column}}@media(prefers-reduced-motion:reduce){.bar-fill{transition:none}}

.expression-lesson .lesson-nav{grid-template-columns:repeat(6,minmax(0,1fr))}.lesson-goals{padding:16px 20px;background:#eef2ff;border-radius:10px;margin:0 0 20px;line-height:1.7}.lesson-goals summary{cursor:pointer;font-weight:600}.transfer-fields{display:flex;flex-wrap:wrap;gap:12px;margin:18px 0}.transfer-fields label{display:flex;flex-direction:column;gap:8px;font-size:15px}.transfer-fields input{width:78px}.transfer-fields label>span{display:flex;gap:6px;align-items:center}@media(max-width:760px){.expression-lesson .lesson-nav{grid-template-columns:repeat(3,minmax(0,1fr))}.expression-lesson .lesson-nav button{font-size:14px;padding:10px 8px}}