@keyframes _si{from{opacity:0}to{opacity:1}}

.legacy-content .lesson-header .kicker {color:var(--ds)}.legacy-content .l-callout b {color:var(--ds)}.legacy-content .tri-box {background:var(--card);border:1.5px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow-card);overflow:hidden}.legacy-content .tri-tabs {display:flex;border-bottom:1px solid var(--border);background:rgba(0,0,0,.015)}.legacy-content .tri-tab {flex:1;padding:12px 8px;border:none;background:none;font-family:inherit;font-size:13.5px;font-weight:800;color:var(--sub);cursor:pointer;border-bottom:2.5px solid transparent;transition:color .15s,border-color .15s}.legacy-content .tri-tab:hover {color:var(--text)}.legacy-content .tri-tab.active {color:var(--ds);border-bottom-color:var(--ds)}.legacy-content .tri-stage {padding:18px 22px;min-height:300px}.legacy-content .tri-intro {font-size:12.5px;color:var(--sub);margin-bottom:12px;line-height:1.75}.legacy-content .tri-intro b {color:var(--ds-deep)}.legacy-content .tree-view {font-family:"SF Mono","Fira Code",Menlo,monospace;font-size:13px;line-height:1.4}.legacy-content .tree-view ul {list-style:none;padding-left:24px;margin:0;position:relative}.legacy-content .tree-view > ul {padding-left:0}.legacy-content .tree-view > ul::before {display:none}.legacy-content .tree-view ul ul::before {content:'';position:absolute;left:9px;top:0;bottom:12px;border-left:1.5px solid var(--ds-line)}.legacy-content .tree-view ul ul li {position:relative}.legacy-content .tree-view ul ul li::before {content:'';position:absolute;left:-15px;top:13px;width:13px;border-top:1.5px solid var(--ds-line)}.legacy-content .tn-row {display:inline-flex;align-items:center;gap:6px;padding:3px 8px;border-radius:8px;margin:1px 0;cursor:default;transition:background .12s}.legacy-content .tn-row.has-kids {cursor:pointer}.legacy-content .tn-row.has-kids:hover {background:var(--ds-soft)}.legacy-content .tn-arrow {width:12px;font-size:9px;color:var(--ds);transition:transform .2s;display:inline-block;text-align:center;flex-shrink:0}.legacy-content .tn-node.closed > .tn-row .tn-arrow {transform:rotate(-90deg)}.legacy-content .tn-node.closed > ul {display:none}.legacy-content .tn-label {font-weight:600;color:var(--text)}.legacy-content .tn-note {font-size:11px;color:var(--sub);font-family:-apple-system,BlinkMacSystemFont,"PingFang SC",sans-serif}.legacy-content .tn-badge {font-size:10px;font-weight:800;padding:1px 7px;border-radius:99px;font-family:-apple-system,BlinkMacSystemFont,"PingFang SC",sans-serif;flex-shrink:0}.legacy-content .tn-badge.root {background:var(--ds);color:#fff}.legacy-content .tn-badge.leaf {background:rgba(22,163,74,.12);color:var(--success)}.legacy-content .tri-legend {display:flex;gap:16px;flex-wrap:wrap;padding:12px 22px;border-top:1px dashed var(--border);font-size:12px;color:var(--sub)}.legacy-content .tri-legend span b {color:var(--text)}.legacy-content .ast-box {background:var(--card);border:1.5px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow-card);overflow:hidden}.legacy-content .ast-code {padding:18px 22px;border-bottom:1px solid var(--border);background:rgba(0,0,0,.02);font-family:"SF Mono","Fira Code",Menlo,monospace;font-size:17px;text-align:center;letter-spacing:.5px}.legacy-content .ast-code .tk {padding:3px 5px;border-radius:6px;color:var(--text);transition:background .25s,color .25s}.legacy-content .ast-code .tk.lit {background:var(--ds);color:#fff}.legacy-content .ast-code .tk.done {background:var(--ds-soft);color:var(--ds-deep)}.legacy-content .ast-code .tk.picked {background:var(--amber);color:#fff}.legacy-content .ast-stage {padding:10px 12px 4px;display:flex;justify-content:center}.legacy-content .ast-stage svg {width:100%;max-width:560px;height:auto;display:block}.legacy-content .ast-g {opacity:0;transform:translateY(14px);transition:opacity .55s ease,transform .55s ease}.legacy-content .ast-g.on {opacity:1;transform:translateY(0)}.legacy-content .ast-edge {stroke:var(--ds-line);stroke-width:2}.legacy-content .ast-op {fill:var(--ds)}.legacy-content .ast-op-txt {fill:#fff;font-size:19px;font-weight:800;font-family:"SF Mono",Menlo,monospace}.legacy-content .ast-leaf {fill:#fff;stroke:var(--ds-line);stroke-width:1.5}.legacy-content .ast-leaf-txt {fill:var(--text);font-size:13px;font-weight:700;font-family:"SF Mono",Menlo,monospace}.legacy-content .ast-node {cursor:default}.legacy-content svg.clickable .ast-node {cursor:pointer}.legacy-content .ast-node.picked .ast-op {fill:var(--amber)}.legacy-content .ast-node.picked .ast-leaf {stroke:var(--amber);stroke-width:2.5}.legacy-content .ast-tag {fill:var(--sub);font-size:10.5px;font-weight:700}.legacy-content .ast-narr {margin:0 22px;padding:12px 16px;background:var(--ds-soft);border:1.5px dashed var(--ds-line);border-radius:var(--radius-sm);font-size:13px;line-height:1.75;color:var(--sub);min-height:46px}.legacy-content .ast-narr b {color:var(--ds-deep)}.legacy-content .ast-foot {display:flex;align-items:center;gap:12px;flex-wrap:wrap;padding:14px 22px}.legacy-content .btn-ds {background:var(--ds);color:#fff;border:none;padding:10px 26px;border-radius:999px;font-size:14px;font-weight:800;cursor:pointer;font-family:inherit;transition:filter .15s,transform .15s}.legacy-content .btn-ds:hover:not(:disabled) {filter:brightness(1.08);transform:translateY(-1px)}.legacy-content .btn-ds:disabled {background:#c4c8cf;cursor:not-allowed}.legacy-content .ast-status {font-size:12.5px;color:var(--sub);font-weight:600}.legacy-content .link-grid {display:grid;grid-template-columns:1fr 1fr;gap:14px}.legacy-content .link-card {background:var(--card);border:1.5px solid var(--border);border-radius:var(--radius);padding:18px 20px;box-shadow:var(--shadow-card)}.legacy-content .link-card .lk-icon {font-size:24px;margin-bottom:8px}.legacy-content .link-card h4 {font-size:15px;font-weight:800;color:var(--text);margin-bottom:6px}.legacy-content .link-card p {font-size:13px;color:var(--sub);line-height:1.75}.legacy-content .link-card p b {color:var(--ds-deep)}.legacy-content .takeaway-box {background:linear-gradient(135deg,#f0f9ff,#e0f2fe);border:1.5px solid #bae6fd;border-radius:var(--radius);padding:24px 28px;margin-top:36px}.legacy-content .takeaway-box h3 {font-size:17px;font-weight:800;color:var(--ds-deep);margin-bottom:10px}.legacy-content .takeaway-box ul {list-style:none;padding:0;margin:0}.legacy-content .takeaway-box li {font-size:14.5px;color:#0c4a6e;line-height:1.8;padding:4px 0 4px 22px;position:relative}.legacy-content .takeaway-box li::before {content:'';position:absolute;left:0;top:13px;width:8px;height:8px;border-radius:50%;background:var(--ds)}@media (max-width:768px){.legacy-content .tri-stage {padding:14px 12px}.legacy-content .tree-view {font-size:12px}.legacy-content .ast-code {font-size:14px;padding:14px 10px}.legacy-content .link-grid {grid-template-columns:1fr}}

.legacy-content .xa-tldr {margin:18px 0 4px;padding:14px 18px;background:rgba(0,102,255,0.04);border:1px solid rgba(0,102,255,0.16);border-radius:10px}.legacy-content .xa-tldr .xa-tldr-tag {display:block;font-size:11px;font-weight:800;letter-spacing:1px;color:var(--accent,#0066ff);margin-bottom:6px}.legacy-content .xa-tldr p {margin:0;font-size:15px;line-height:1.8;color:var(--text,#1f2937)}