.concept-intro{display:grid;grid-template-columns:minmax(0,1.15fr) minmax(280px,.85fr);gap:18px;margin:0 0 22px}.concept-intro .card{height:100%}.concept-stack{display:grid;gap:10px}.concept-step{display:flex;gap:12px;align-items:flex-start;padding:12px 0;border-bottom:1px solid var(--line)}.concept-step:last-child{border-bottom:0}.concept-num{width:28px;height:28px;border-radius:9px;background:var(--brand-soft);color:var(--brand-dark);display:grid;place-items:center;font-size:12px;font-weight:800;flex:0 0 auto}.concept-step strong{display:block;font-size:14px;margin-bottom:2px}.concept-step span{display:block;color:var(--muted);font-size:13px}.deep-dive{border-top:1px solid var(--line);margin-top:18px;padding-top:14px}.deep-dive summary{cursor:pointer;list-style:none;font-weight:680;color:#344054;display:flex;align-items:center;gap:8px}.deep-dive summary::-webkit-details-marker{display:none}.deep-dive summary::before{content:'+';width:20px;height:20px;border:1px solid var(--line-strong);border-radius:6px;display:grid;place-items:center;color:var(--brand);font-size:14px;line-height:1}.deep-dive[open] summary::before{content:'–'}.deep-dive-body{padding:14px 0 0 28px;color:var(--muted);font-size:14px}.deep-dive-body p{margin:0 0 10px}.deep-dive-body ul,.deep-dive-body ol{margin:8px 0 10px 20px}.deep-dive-body li{margin:5px 0}.ai-guide{border:1px solid #d6e1ff;background:linear-gradient(120deg,#f8faff,#fff);border-radius:12px;padding:14px 16px;margin-top:14px;color:#344054;font-size:13px}.ai-guide strong{color:var(--brand-dark)}.ai-guide code{font-family:var(--mono);font-size:12px}.custody-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:16px 0}.custody-card{border:1px solid var(--line);background:#fff;border-radius:12px;padding:16px;cursor:pointer;position:relative}.custody-card:hover{border-color:#98a2b3}.custody-card.selected{border:2px solid var(--brand);background:#f8faff}.custody-card .recommended{display:inline-flex;font-size:10px;text-transform:uppercase;letter-spacing:.05em;color:var(--green);background:var(--green-soft);border:1px solid #abefc6;border-radius:999px;padding:3px 6px;font-weight:800;margin-bottom:8px}.custody-card h4{margin:0 0 6px;font-size:15px}.custody-card p{margin:0;color:var(--muted);font-size:13px}.instruction-list{counter-reset:item;margin:12px 0 0;padding:0;list-style:none}.instruction-list li{counter-increment:item;display:grid;grid-template-columns:28px 1fr;gap:10px;align-items:start;margin:10px 0}.instruction-list li::before{content:counter(item);width:24px;height:24px;border-radius:50%;background:var(--surface-2);color:#475467;display:grid;place-items:center;font-size:11px;font-weight:800}.evidence-note{border-left:3px solid var(--brand);padding:10px 12px;background:#f8faff;color:#475467;border-radius:0 8px 8px 0;margin:12px 0}.warning-note{border-left-color:var(--amber);background:var(--amber-soft)}.root-preview{display:grid;grid-template-columns:150px minmax(0,1fr);gap:8px 14px;font-size:13px}.root-preview dt{color:#667085}.root-preview dd{margin:0;font-weight:650;word-break:break-word}.learn-link{color:var(--brand);font-weight:650;text-decoration:none}.learn-link:hover{text-decoration:underline}@media(max-width:800px){.concept-intro,.custody-grid{grid-template-columns:1fr}.deep-dive-body{padding-left:0}.root-preview{grid-template-columns:1fr}.root-preview dt{margin-top:6px}}
/* teaching layer: (i) buttons, explanation dialog, guide — shared by every page */
.info-i{display:inline-grid;place-items:center;width:20px;height:20px;border-radius:50%;border:1.5px solid var(--brand);background:#fff;color:var(--brand);font:italic 700 12px/1 Georgia,serif;cursor:pointer;vertical-align:middle;margin-left:6px;padding:0;flex:0 0 auto}
.info-i:hover,.info-i:focus-visible{background:var(--brand);color:#fff;outline:none}
.info-i-static{cursor:default;margin:0 2px}
.explain-dialog{border:0;border-radius:16px;padding:0;width:min(640px,calc(100% - 32px));max-height:calc(100% - 48px);box-shadow:0 24px 60px rgba(16,24,40,.25)}
.explain-dialog::backdrop{background:rgba(16,24,40,.45)}
.explain-body{padding:22px 24px 18px;overflow-wrap:anywhere}
.explain-body h2{margin:2px 0 6px;font-size:22px}
.explain-body .lead{color:var(--muted);margin:0 0 14px}
.explain-body h4{margin:14px 0 4px;font-size:13px;text-transform:uppercase;letter-spacing:.05em;color:#475467}
.explain-body p{margin:0}
.explain-body ol{margin:4px 0 0 18px;padding:0}.explain-body li{margin:4px 0}
.explain-proof{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-top:14px}
.explain-proof div{border:1px solid var(--line);border-radius:10px;padding:10px 12px;font-size:13px}
.explain-actions{display:flex;gap:8px;flex-wrap:wrap;padding:14px 24px 20px;border-top:1px solid var(--line)}
.guide-short{color:var(--muted);font-weight:500}
.learn-banner{display:flex;gap:12px;align-items:center;flex-wrap:wrap;margin:0 0 16px;padding:12px 16px;border:1px solid #d6e1ff;border-radius:12px;background:#f8faff;font-size:14px;color:#344054}
@media(max-width:640px){.explain-proof{grid-template-columns:1fr}.explain-body{padding:18px 16px 14px}.explain-actions{padding:12px 16px 16px}}