:root{
  --bg:#eef3f8;--card:#fff;--ink:#172b43;--muted:#63788d;--line:#d8e2ec;
  --green:#08765d;--green2:#0ea77d;--green-soft:#e7f6ef;
  --blue:#175da8;--blue2:#2f7fd0;--blue-soft:#e9f2ff;
  --orange:#b86300;--orange-soft:#fff4e5;--red:#b93545;--red-soft:#fff0f2;
  --shadow:0 16px 45px rgba(28,58,89,.10)
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;color:var(--ink);background:
  radial-gradient(circle at 10% 0%,rgba(8,118,93,.06),transparent 26%),
  radial-gradient(circle at 92% 0%,rgba(23,93,168,.06),transparent 28%),var(--bg);
  font-family:Inter,Pretendard,"Noto Sans KR",system-ui,-apple-system,sans-serif
}
button{font:inherit;cursor:pointer}
.wrap{max-width:1500px;margin:auto;padding:22px}
.hero{background:linear-gradient(135deg,#10283e,#173b58);color:#fff;border-radius:24px;padding:28px 30px;box-shadow:var(--shadow)}
.hero small{display:block;color:#6ce0bb;font-weight:900;letter-spacing:.13em;font-size:12px}
.hero h1{margin:7px 0 8px;font-size:clamp(28px,4vw,48px);letter-spacing:-.04em}
.hero p{margin:0;color:#c8d7e4;line-height:1.7;max-width:900px}
.start-guide{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-top:20px}
.guide-step{display:flex;align-items:center;gap:10px;padding:13px 14px;border:1px solid rgba(255,255,255,.13);background:rgba(255,255,255,.055);border-radius:14px}
.guide-step b{display:grid;place-items:center;flex:0 0 30px;height:30px;border-radius:50%;background:#6ce0bb;color:#0b352c}
.guide-step span{font-size:13px;color:#e7f0f7}.guide-step strong{display:block;color:#fff;font-size:14px}

.lesson-tabs{margin:16px 0;display:flex;gap:8px;overflow:auto;padding-bottom:2px}
.lesson-tab{white-space:nowrap;border:1px solid var(--line);background:#fff;color:var(--ink);border-radius:999px;padding:10px 14px;font-weight:800;font-size:13px}
.lesson-tab.active{border-color:var(--green);background:var(--green);color:#fff}
.lesson-tab.completed{position:relative;padding-right:34px}
.lesson-tab.completed::after{content:"✓";position:absolute;right:11px;top:50%;transform:translateY(-50%);width:17px;height:17px;border-radius:50%;display:grid;place-items:center;background:#0ea77d;color:#fff;font-size:10px}
.lesson-tab.active.completed::after{background:#fff;color:var(--green)}

.course-progress{display:grid;grid-template-columns:auto minmax(220px,1fr) auto;gap:14px;align-items:center;margin:0 0 12px;padding:13px 15px;background:#fff;border:1px solid var(--line);border-radius:16px;box-shadow:var(--shadow)}
.course-progress strong{font-size:13px}.course-progress small{display:block;color:var(--muted);font-size:10px;margin-top:2px}
.course-bar{height:9px;border-radius:999px;background:#e8eef3;overflow:hidden}
.course-bar>div{height:100%;width:0;background:linear-gradient(90deg,var(--green2),var(--blue2));transition:.3s}
.course-count{font-size:12px;font-weight:1000;color:#486176;white-space:nowrap}

.view-mode-card{display:flex;justify-content:space-between;gap:16px;align-items:center;margin:0 0 12px;padding:13px 15px;background:#f8fbfd;border:1px solid #d5e2ea;border-radius:16px;box-shadow:var(--shadow)}
.view-mode-copy strong{display:block;font-size:13px}.view-mode-copy span{display:block;margin-top:3px;color:#667e91;font-size:10px;line-height:1.5}
.view-mode-actions{display:flex;gap:7px;flex:0 0 auto}
.view-mode-btn{min-width:132px;border:1px solid #cfdae4;background:#fff;color:#456176;border-radius:11px;padding:8px 11px;text-align:left}
.view-mode-btn b{display:block;font-size:11px}.view-mode-btn small{display:block;margin-top:2px;color:#8093a5;font-size:8px}
.view-mode-btn.active,.view-mode-btn[aria-pressed="true"]{border-color:#2c759c;background:#edf7fb;color:#154e6d}
.view-mode-btn.active small,.view-mode-btn[aria-pressed="true"] small{color:#4b7187}

.lab-scope-strip{display:grid;gap:5px;margin:0 0 12px;padding:12px 14px;border:1px solid #d8e2ec;border-radius:14px;background:#fff;color:#61788b;font-size:10px;line-height:1.6;box-shadow:var(--shadow)}
.lab-scope-strip>b{color:#173b58;font-size:11px}
.lab-scope-strip span b{color:#8a5b0a}

.start-state-strip{display:grid;grid-template-columns:1fr 1fr;gap:8px;margin:-2px 0 12px}
.start-state-strip>div{padding:10px 12px;border:1px solid #dce6ee;border-radius:12px;background:#f8fbfd}
.start-state-strip small{display:block;color:#7890a3;font-size:8px;font-weight:1000;letter-spacing:.07em}
.start-state-strip strong{display:block;margin-top:4px;font-size:11px;line-height:1.5}

.mobile-flow{display:none}

.arp-field-strip{margin-top:10px;padding:12px 13px;border:1px solid #b9d9ce;border-radius:13px;background:#f5fcf9}
.arp-field-strip[hidden]{display:none!important}
.arp-field-head{display:flex;justify-content:space-between;gap:12px;align-items:center;margin-bottom:9px}
.arp-field-head b{font-size:11px;color:#08765d}.arp-field-head span{color:#657f72;font-size:9px;line-height:1.45;text-align:right}
.arp-field-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:7px}
.arp-field-grid>div{padding:9px;border:1px solid #d5e6df;border-radius:10px;background:#fff;min-width:0}
.arp-field-grid small{display:block;color:#789085;font-size:8px;font-weight:900}
.arp-field-grid strong{display:block;margin-top:4px;font:700 10px/1.45 ui-monospace,SFMono-Regular,Consolas,monospace;word-break:break-all}

.evidence-link-row{display:flex;justify-content:space-between;align-items:center;gap:12px;margin-top:10px;padding:10px 12px;border:1px dashed #cbd9e4;border-radius:11px;background:#fbfdff}
.evidence-link-row a{color:#175da8;font-size:10px;font-weight:900;text-decoration:none}.evidence-link-row a:hover{text-decoration:underline}
.evidence-link-row span{color:#7a90a3;font-size:9px;line-height:1.45;text-align:right}

.manual-state-warning{margin-bottom:10px;padding:10px 11px;border-left:4px solid #b86300;border-radius:10px;background:#fff7eb;color:#6d532b;font-size:10px;line-height:1.55}

.card{background:var(--card);border:1px solid var(--line);border-radius:20px;box-shadow:var(--shadow)}
.lab-card{padding:18px}
.coach{display:grid;grid-template-columns:auto 1fr auto;gap:14px;align-items:center;border:1px solid #bcd7cc;background:#f2fbf7;border-radius:16px;padding:14px 16px;margin-bottom:14px}
.coach-icon{width:42px;height:42px;border-radius:13px;background:var(--green);color:#fff;display:grid;place-items:center;font-weight:1000}
.coach-title{font-weight:900;font-size:16px}.coach-text{color:#567062;font-size:13px;margin-top:3px;line-height:1.5}
.hint-trigger{border:1px solid #9ac8ba;background:#fff;color:#08765d;border-radius:11px;padding:9px 11px;font-size:11px;font-weight:1000;white-space:nowrap}
.hint-box{display:none;margin:-4px 0 14px;padding:12px 14px;border:1px solid #edd3a6;background:#fff8eb;border-radius:13px;color:#6d532b;font-size:12px;line-height:1.65}
.hint-box.show{display:block}

.topology-shell{position:relative;overflow:hidden;border-radius:18px;border:1px solid #cbd8e4;background:linear-gradient(180deg,#f8fbfd,#eef4f8)}
.topology-shell svg{display:block;width:100%;height:auto}
.topology-link{fill:none;stroke:#9db1c2;stroke-width:8;stroke-linecap:round;transition:stroke .2s,stroke-width .2s,filter .2s,stroke-dasharray .2s}
.topology-link.ingress{stroke:var(--green2);stroke-width:11;filter:drop-shadow(0 0 6px rgba(14,167,125,.35));stroke-dasharray:16 10;animation:dash 1s linear infinite}
.topology-link.egress{stroke:var(--blue2);stroke-width:11;filter:drop-shadow(0 0 6px rgba(47,127,208,.35));stroke-dasharray:16 10;animation:dash 1s linear infinite reverse}
.topology-link.flood{stroke:var(--orange);filter:drop-shadow(0 0 6px rgba(184,99,0,.25))}
@keyframes dash{to{stroke-dashoffset:-52}}
.port-label{fill:#6d8395;font-size:17px;font-weight:900}
.device rect{fill:#fff;stroke:#cbd9e4;stroke-width:2}.device.switch rect{fill:#f0f7fb;stroke:#97b9cf}
.device text{fill:#496377;font-size:15px}.device-title{fill:#173b58!important;font-size:22px!important;font-weight:1000}
.device-mac{font:12px ui-monospace,SFMono-Regular,Consolas,monospace!important;fill:#6b8091!important}
.device-sub{font-size:12px!important;fill:#8295a6!important}.switch-badge{font-size:12px!important;font-weight:1000;fill:var(--green)!important}

.link-legend{display:flex;gap:14px;flex-wrap:wrap;margin:9px 2px 0;color:#687f92;font-size:10px;align-items:center}
.link-legend span{display:flex;align-items:center;gap:6px}.link-legend b{color:#49657a}
.legend-line{display:inline-block;width:28px;height:0;border-top:5px solid;border-radius:5px}.legend-line.ingress{border-color:var(--green2)}.legend-line.egress{border-color:var(--blue2)}

.live-event-strip{min-height:74px;margin-top:12px;border:1px solid #d5e2ea;background:#fff;border-radius:14px;display:grid;grid-template-columns:auto minmax(0,1fr) auto;gap:12px;align-items:center;padding:11px 13px;transition:.2s}
.live-event-icon{width:38px;height:38px;border-radius:11px;display:grid;place-items:center;background:#eef3f7;color:#597185;font-size:12px;font-weight:1000}
.live-event-main b{display:block;font-size:13px}.live-event-main p{margin:3px 0 0;color:#6a8092;font-size:11px;line-height:1.55}
.live-event-kind{border-radius:999px;padding:6px 9px;background:#eef3f7;color:#607587;font-size:9px;font-weight:1000;letter-spacing:.06em;white-space:nowrap}
.live-event-strip.learning{border-color:#a9d8c8;background:#f5fcf9}.live-event-strip.learning .live-event-icon,.live-event-strip.learning .live-event-kind{background:#dff5ed;color:#08765d}
.live-event-strip.known{border-color:#b8d2ed;background:#f5f9fe}.live-event-strip.known .live-event-icon,.live-event-strip.known .live-event-kind{background:#e5f0ff;color:#175da8}
.live-event-strip.flood{border-color:#edc98f;background:#fff9ef}.live-event-strip.flood .live-event-icon,.live-event-strip.flood .live-event-kind{background:#fff0d5;color:#95540a}
.live-event-strip.broadcast{border-color:#d9c6ef;background:#faf7ff}.live-event-strip.broadcast .live-event-icon,.live-event-strip.broadcast .live-event-kind{background:#eee4fb;color:#674593}
.live-event-strip.aging{border-color:#e4b1b8;background:#fff5f6}.live-event-strip.aging .live-event-icon,.live-event-strip.aging .live-event-kind{background:#ffe7ea;color:#ad3443}
.live-event-strip.filter{border-color:#c8d5e0;background:#f7fafc}.live-event-strip.filter .live-event-icon,.live-event-strip.filter .live-event-kind{background:#e8eef4;color:#365a74}

.basic-state-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:9px;margin-top:12px}
.basic-state-grid article{padding:12px 13px;border:1px solid #dce6ee;border-radius:13px;background:#fbfdff;min-width:0}
.basic-state-grid small{display:block;color:#7b8fa0;font-size:9px;font-weight:900;letter-spacing:.05em}
.basic-state-grid strong{display:block;margin:6px 0;font:700 12px/1.45 ui-monospace,SFMono-Regular,Consolas,monospace;word-break:break-all}
.basic-state-grid span{display:block;color:#718698;font-size:10px;line-height:1.45}

.controls{display:flex;justify-content:flex-end;gap:9px;margin-top:14px}
.run-btn,.age-btn{border:0;border-radius:14px;padding:14px 22px;font-weight:1000}
.run-btn{background:linear-gradient(135deg,#0ea77d,#08765d);color:#fff;box-shadow:0 10px 24px rgba(8,118,93,.22)}
.age-btn{border:1px solid #e2b56a;background:#fff8eb;color:#8a5b0a}
.run-btn:disabled,.age-btn:disabled{opacity:.45;cursor:not-allowed;box-shadow:none}

.event-timeline{display:flex;gap:8px;overflow:auto;margin-top:12px;padding:2px 0 5px}
.timeline-empty{width:100%;border:1px dashed #cbd8e3;border-radius:12px;padding:11px;color:#7a90a3;font-size:11px;text-align:center}
.timeline-item{flex:0 0 auto;min-width:180px;max-width:245px;border:1px solid #dbe5ed;border-radius:12px;padding:9px 10px;background:#fff}
.timeline-item small{display:block;color:#8295a5;font-size:8px;font-weight:1000;letter-spacing:.06em}
.timeline-item b{display:block;margin-top:4px;font-size:11px}.timeline-item span{display:block;margin-top:3px;color:#708698;font-size:9px;line-height:1.45}
.timeline-item.known{border-top:3px solid var(--blue2)}.timeline-item.flood{border-top:3px solid var(--orange)}.timeline-item.broadcast{border-top:3px solid #7b56ae}.timeline-item.learning{border-top:3px solid var(--green2)}.timeline-item.aging{border-top:3px solid var(--red)}.timeline-item.filter{border-top:3px solid #6b7f90}

.result-title{display:flex;justify-content:space-between;align-items:center;gap:12px;margin:22px 2px 10px}
.result-title h2{font-size:19px;margin:0}.result-title span{font-size:12px;color:var(--muted)}
.flow{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}
.flow-step{min-height:112px;border:1px solid var(--line);border-radius:15px;padding:13px;background:#fbfdff;position:relative;overflow:hidden}
.flow-step .n{font-size:10px;letter-spacing:.08em;color:#8295a8;font-weight:900}
.flow-step strong{display:block;font-size:14px;margin:7px 0 5px}.flow-step p{font-size:12px;line-height:1.5;color:var(--muted);margin:0}
.flow-step.active{border-color:#6cbda8;background:#f1fbf7}.flow-step.done::after{content:"✓";position:absolute;right:11px;top:9px;color:var(--green);font-weight:1000}
.explain{margin-top:12px;border-radius:15px;padding:14px 16px;border-left:5px solid var(--green);background:#f5faf8;font-size:13px;line-height:1.65;color:#425b4f}
.explain.flood{border-left-color:var(--orange);background:#fff9ef;color:#6f542d}.explain.broadcast{border-left-color:#7652a4;background:#faf7ff;color:#604877}

.lesson-status{margin-top:12px;border:1px solid #d8e2ec;background:#fbfdff;border-radius:15px;padding:13px 14px}
.lesson-status-head{display:flex;justify-content:space-between;gap:10px;align-items:center}.lesson-status-head strong{font-size:13px}
.status-badge{border-radius:999px;padding:5px 9px;background:#edf2f6;color:#607587;font-size:10px;font-weight:1000}
.status-badge.success{background:#dff5ed;color:#08765d}
.check-list{display:grid;grid-template-columns:repeat(4,1fr);gap:8px;margin-top:10px}
.check-item{display:flex;gap:8px;align-items:flex-start;border:1px solid #e0e8ef;background:#fff;border-radius:11px;padding:9px}
.check-dot{flex:0 0 20px;height:20px;border-radius:50%;display:grid;place-items:center;background:#eef3f7;color:#8ba0b2;font-size:10px;font-weight:1000}
.check-item.done{border-color:#b8dece;background:#f5fcf9}.check-item.done .check-dot{background:#0ea77d;color:#fff}
.check-item b{display:block;font-size:10px}.check-item span{display:block;color:#7b8fa0;font-size:9px;line-height:1.35;margin-top:2px}
.verdict{margin-top:9px;padding:9px 11px;border-radius:10px;background:#f4f7f9;color:#5d7284;font-size:11px;line-height:1.55}
.verdict.success{background:#eaf8f2;color:#316655}
.next-row{display:flex;justify-content:flex-end;gap:8px;margin-top:12px}
.soft-btn,.next-btn{border:1px solid var(--line);background:#fff;border-radius:12px;padding:10px 14px;color:var(--ink);font-weight:800}
.next-btn{background:#163b58;color:#fff;border-color:#163b58}.next-btn:disabled{opacity:.42;cursor:not-allowed;background:#8394a3;border-color:#8394a3}

.course-complete{display:none;margin-top:16px;padding:20px;border-radius:19px;border:1px solid #a8d7c7;background:linear-gradient(135deg,#edf9f5,#eef5fd);box-shadow:var(--shadow)}
.course-complete.show{display:block}.course-complete .eyebrow2{font-size:10px;letter-spacing:.12em;color:#08765d;font-weight:1000}
.course-complete h2{margin:6px 0 6px;font-size:24px}.course-complete p{margin:0;color:#567083;font-size:12px;line-height:1.65}
.completion-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:9px;margin-top:13px}
.completion-card{background:#fff;border:1px solid #d7e5e0;border-radius:12px;padding:11px}.completion-card b{display:block;font-size:12px}.completion-card span{display:block;font-size:10px;color:#718698;line-height:1.4;margin-top:3px}
.next-lab-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}.next-lab-actions a{text-decoration:none;border:1px solid #cfdce6;background:#fff;color:#173b58;border-radius:11px;padding:10px 13px;font-size:11px;font-weight:900}.next-lab-actions a.primary{background:#173b58;color:#fff;border-color:#173b58}

.details-grid{display:grid;grid-template-columns:1fr 1fr 1fr;gap:14px;margin-top:14px}
details.panel{background:#fff;border:1px solid var(--line);border-radius:17px;box-shadow:var(--shadow);overflow:hidden}
details.panel summary{list-style:none;padding:16px 18px;font-weight:900;cursor:pointer;display:flex;justify-content:space-between;align-items:center;gap:10px}
details.panel summary span{font-weight:500;color:#7b8fa1;font-size:10px}details.panel summary::-webkit-details-marker{display:none}
details.panel summary::after{content:"＋";color:#60768a;font-size:18px}details.panel[open] summary::after{content:"－"}
.panel-body{border-top:1px solid var(--line);padding:16px}
.table-title{display:flex;justify-content:space-between;align-items:center;gap:10px}.table-title.spaced{margin-top:18px}.table-title strong{font-size:12px}.table-title span{color:#7a90a3;font-size:10px}
.table-title button{border:1px solid #cfdce5;background:#fff;color:#536e82;border-radius:9px;padding:6px 8px;font-size:9px;font-weight:900}
.state-table{width:100%;border-collapse:collapse;margin-top:10px;font-size:11px}.state-table th,.state-table td{padding:8px;border-bottom:1px solid #e3eaf0;text-align:left}.state-table th{font-size:9px;color:#7a90a3}
.state-table code{font:10px ui-monospace,SFMono-Regular,Consolas,monospace}.empty-row{color:#7a90a3}
.panel-note{margin:12px 0 0;padding:10px 11px;border-radius:10px;background:#f1f7fb;color:#587083;font-size:10px;line-height:1.55}
.manual-grid{display:grid;grid-template-columns:1fr 1fr;gap:8px}.manual-grid button{border:1px solid #d5e1ea;background:#fff;border-radius:10px;padding:10px;font-size:10px;font-weight:900;color:#36576e}
.manual-grid button:hover{border-color:#8ab7d3;background:#f5f9fc}
.scope-note{margin-top:12px;padding:11px 12px;border-radius:11px;background:#fff8eb;border:1px solid #ecd3a8;color:#6d532b;font-size:10px;line-height:1.6}
.event-log{min-height:180px;max-height:320px;overflow:auto;padding:12px;border-radius:12px;background:#07131f;color:#d7e3ec;white-space:pre-wrap;font:10px/1.65 ui-monospace,SFMono-Regular,Consolas,monospace}

.footer{padding:22px 0 8px;text-align:center;color:#7b8fa1;font-size:11px;line-height:1.6}

body[data-sim-mode="basic"] .advanced-only{display:none!important}

button:focus-visible,a:focus-visible,summary:focus-visible{outline:3px solid #d98a00;outline-offset:3px}

@media(max-width:1100px){
  .basic-state-grid{grid-template-columns:1fr 1fr}.details-grid{grid-template-columns:1fr}.check-list{grid-template-columns:1fr 1fr}
}
@media(max-width:760px){
  .wrap{padding:10px}.hero{padding:20px;border-radius:18px}.start-guide{grid-template-columns:1fr}
  .course-progress{grid-template-columns:1fr}.view-mode-card{display:grid;grid-template-columns:1fr;gap:9px;padding:11px}
  .view-mode-actions{display:grid;grid-template-columns:1fr 1fr;width:100%}.view-mode-btn{min-width:0;width:100%}
  .coach{grid-template-columns:auto 1fr}.hint-trigger{grid-column:1/-1;width:100%}
  .topology-shell{overflow-x:auto;overscroll-behavior-x:contain}.topology-shell svg{width:920px;max-width:none}
  .mobile-flow{display:grid;grid-template-columns:minmax(90px,.8fr) auto minmax(120px,1fr) auto minmax(0,1.5fr);gap:7px;align-items:center;margin:10px 0;padding:10px;border:1px solid #d7e3eb;border-radius:13px;background:#f8fbfd}
  .mobile-flow>div:not(.mobile-egress){padding:8px;border:1px solid #dfe8ef;border-radius:10px;background:#fff}
  .mobile-flow small{display:block;color:#7a90a3;font-size:7px;font-weight:1000;letter-spacing:.06em}.mobile-flow strong{display:block;margin-top:3px;font-size:10px;line-height:1.4}
  .mobile-flow>i{font-style:normal;color:#5a7487;font-weight:1000;text-align:center}
  .mobile-egress{display:grid;grid-template-columns:repeat(3,1fr);gap:5px}.mobile-egress span{padding:7px;border:1px solid #dfe8ef;border-radius:9px;background:#fff}.mobile-egress b{display:block;margin-top:3px;font-size:8px;line-height:1.35}
  .start-state-strip{grid-template-columns:1fr}.arp-field-grid{grid-template-columns:1fr 1fr}.evidence-link-row{display:grid}.evidence-link-row span{text-align:left}
  .live-event-strip{grid-template-columns:auto 1fr}.live-event-kind{grid-column:2;justify-self:start}
  .basic-state-grid{grid-template-columns:1fr}.controls{display:grid;grid-template-columns:1fr}.run-btn,.age-btn{width:100%}
  .flow{grid-template-columns:1fr}.check-list{grid-template-columns:1fr}.completion-grid{grid-template-columns:1fr}
  .next-row{display:grid;grid-template-columns:1fr 1fr}.next-row button{width:100%}
}
@media(max-width:430px){
  .view-mode-actions{grid-template-columns:1fr}.next-row{grid-template-columns:1fr}.manual-grid{grid-template-columns:1fr}
}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}
}


/* V3 · ARP simulator visual language for MAC topology */
.topology-shell{position:relative;overflow:hidden;border-radius:18px;border:1px solid #cbd8e4;background:#f4f7fb}
.topology-shell svg{display:block;width:100%;height:auto}
.topology-link{transition:stroke .2s,stroke-width .2s,opacity .2s,filter .2s;stroke-linecap:round}
.topology-link.link-up{opacity:1}
.topology-link.ingress{stroke:#12a57e!important;stroke-width:7!important;filter:drop-shadow(0 0 5px rgba(18,165,126,.28))}
.topology-link.egress{stroke:#2f7fd0!important;stroke-width:7!important;filter:drop-shadow(0 0 5px rgba(47,127,208,.24))}
.topology-link.flood{stroke:#b86300!important;stroke-width:7!important;filter:drop-shadow(0 0 5px rgba(184,99,0,.22))}
.mac-trace{display:none;fill:none;stroke-width:7;stroke-linecap:round;stroke-linejoin:round;pointer-events:none;opacity:.78}
.mac-trace.show{display:block}
.mac-trace.trace-in{stroke:#12a57e;marker-end:url(#traceArrowIn)}
.mac-trace.trace-out{stroke:#2f7fd0;marker-end:url(#traceArrowOut)}
.mac-trace.flood{stroke:#b86300;marker-end:url(#traceArrowFlood)}
.port-chip rect{fill:#fff;stroke:#a7b8ca;stroke-width:1.3}
.port-chip text{fill:#172b43;font-size:13px;font-family:Consolas,monospace;font-weight:800}
.svg-fdb-panel rect{fill:#fff;stroke:#7f99b5;stroke-width:2}
.svg-fdb-title{fill:#405a70;font-size:12px;font-weight:900;letter-spacing:.06em}
.svg-fdb-row{fill:#172b43;font-size:13px;font-family:Consolas,monospace;font-weight:700}
.svg-lookup-row{fill:#08765d;font-size:12px;font-family:Consolas,monospace;font-weight:900}
.receive-badge rect{fill:#e7f6ef;stroke:#88ccb6;stroke-width:1.5}
.receive-badge text{fill:#08765d;font-size:10px;font-weight:1000}
.receive-badge.muted rect{fill:#eef3f7;stroke:#c9d5df}
.receive-badge.muted text{fill:#657b8d}
.receive-badge.active rect{fill:#e9f2ff;stroke:#8fb8e1;stroke-width:2}
.receive-badge.active text{fill:#175da8}
.receive-badge.flood rect{fill:#fff4e5;stroke:#e2ad61;stroke-width:2}
.receive-badge.flood text{fill:#9a5b0d}
.packet-sprite{display:none;pointer-events:none;filter:url(#packetGlow)}
.packet-sprite.show{display:block}
.packet-sprite rect{fill:#e0f5ed;stroke:#0ea77d;stroke-width:2}
.packet-sprite circle{fill:#0ea77d}
.packet-sprite text{fill:#075a43;font-size:11px;font-weight:1000}
.packet-sprite.out rect{fill:#e7f0ff;stroke:#2f7fd0}
.packet-sprite.out circle{fill:#2f7fd0}
.packet-sprite.out text{fill:#175da8}
.packet-sprite.out.flood rect{fill:#fff0d5;stroke:#b86300}
.packet-sprite.out.flood circle{fill:#b86300}
.packet-sprite.out.flood text{fill:#8b530e}

@media(max-width:760px){
  .topology-shell{overflow-x:auto;overscroll-behavior-x:contain}
  .topology-shell svg{width:1080px;max-width:none}
}
@media(prefers-reduced-motion:reduce){
  .packet-sprite{filter:none}
}


/* V4 · beginner-first visual simplification */
.coach-main{min-width:0}
.coach-state{display:flex;gap:7px;flex-wrap:wrap;margin-top:8px}
.coach-state span{display:inline-flex;align-items:center;gap:6px;padding:5px 8px;border:1px solid #cfe0d9;border-radius:999px;background:#fff;color:#527066;font-size:9px;line-height:1.3}
.coach-state b{color:#08765d;font-size:8px;letter-spacing:.05em}
.coach-state strong{font-size:9px;font-weight:800;color:#36584d}

body[data-sim-mode="basic"] .topology-detail{display:none!important}
.svg-fdb-panel{display:none!important}

.topology-shell{
  max-width:1180px;
  margin:0 auto;
  background:#f4f7fb;
}
body[data-sim-mode="advanced"] .topology-shell{max-width:1280px}

.svg-decision-panel rect{fill:#07131f;stroke:#44657d;stroke-width:2}
.svg-decision-title{fill:#8aa9bc;font-size:12px;font-weight:1000;letter-spacing:.07em}
.svg-decision-row{fill:#d8e6ef;font-size:15px;font-family:Consolas,monospace;font-weight:800}
.svg-decision-action{fill:#6ce0bb;font-size:16px;font-family:Consolas,monospace;font-weight:1000}

.controls{
  max-width:1180px;
  margin:12px auto 0;
  display:flex;
  justify-content:center;
  align-items:center;
  gap:10px;
}
.run-btn{min-width:330px;padding:16px 28px;font-size:16px}
.age-btn{padding:15px 20px}

.link-legend{
  max-width:1180px;
  margin:8px auto 0;
  justify-content:center;
  padding:0 8px;
}
.live-event-strip{
  max-width:1180px;
  margin:10px auto 0;
}
.explain{
  max-width:1180px;
  margin:10px auto 0;
}
.lesson-status{
  max-width:1180px;
  margin:12px auto 0;
}
.next-row{
  max-width:1180px;
  margin:12px auto 0;
}

.packet-sprite rect{width:124px;transform:translateX(-12px)}
.packet-sprite text{font-size:13px}

body[data-sim-mode="basic"] .result-title,
body[data-sim-mode="basic"] .flow,
body[data-sim-mode="basic"] .basic-state-grid,
body[data-sim-mode="basic"] .arp-field-strip,
body[data-sim-mode="basic"] .event-timeline,
body[data-sim-mode="basic"] .evidence-link-row,
body[data-sim-mode="basic"] .lab-scope-strip{display:none!important}

@media(max-width:760px){
  .topology-shell{display:none!important}
  .link-legend{display:none}
  .mobile-flow{
    display:grid;
    grid-template-columns:1fr;
    gap:6px;
    max-width:560px;
    margin:8px auto 0;
    padding:10px;
    border:1px solid #d7e3eb;
    border-radius:14px;
    background:#f8fbfd
  }
  .mobile-flow>div:not(.mobile-egress){
    padding:10px 12px;
    border:1px solid #dfe8ef;
    border-radius:11px;
    background:#fff;
    text-align:center
  }
  .mobile-flow>i{
    transform:rotate(90deg);
    font-style:normal;
    color:#5a7487;
    font-weight:1000;
    text-align:center;
    line-height:1
  }
  .mobile-egress{
    display:grid;
    grid-template-columns:repeat(3,minmax(0,1fr));
    gap:5px
  }
  .mobile-egress span{
    padding:9px 6px;
    border:1px solid #dfe8ef;
    border-radius:10px;
    background:#fff;
    text-align:center;
    min-width:0
  }
  .mobile-flow small{display:block;color:#7a90a3;font-size:8px;font-weight:1000;letter-spacing:.06em}
  .mobile-flow strong{display:block;margin-top:3px;font-size:12px;line-height:1.4}
  .mobile-egress b{display:block;margin-top:3px;font-size:9px;line-height:1.35;overflow-wrap:anywhere}

  .controls{display:grid;grid-template-columns:1fr;max-width:560px;margin:10px auto 0}
  .run-btn,.age-btn{width:100%;min-width:0}
  .live-event-strip,.explain,.lesson-status,.next-row{max-width:560px}
  .coach-state{display:grid;grid-template-columns:1fr}
  .coach-state span{border-radius:10px;justify-content:flex-start}
}

@media(max-width:430px){
  .mobile-egress{grid-template-columns:1fr}
}


/* V6 · education-first prediction flow */
.beginner-key{
  max-width:1180px;
  margin:0 auto 12px;
  padding:11px 14px;
  display:flex;
  gap:8px 14px;
  align-items:center;
  flex-wrap:wrap;
  border:1px solid #cfe0d9;
  border-radius:13px;
  background:#f5fbf8;
  color:#4f6a60;
  font-size:11px;
  line-height:1.55
}
.beginner-key>b{color:#08765d;white-space:nowrap}
.beginner-key strong{color:#173b58}

.prediction-card{
  max-width:1180px;
  margin:0 auto 12px;
  padding:16px;
  border:2px solid #c6d8e5;
  border-radius:16px;
  background:#fff;
}
.prediction-copy small{
  display:block;
  color:#175da8;
  font-size:10px;
  font-weight:1000;
  letter-spacing:.04em
}
.prediction-copy h2{
  margin:5px 0 4px;
  font-size:18px;
  line-height:1.4;
  letter-spacing:-.02em
}
.prediction-copy p{
  margin:0;
  color:#6d8192;
  font-size:11px;
  line-height:1.55
}
.prediction-options{
  display:grid;
  grid-template-columns:repeat(3,minmax(0,1fr));
  gap:8px;
  margin-top:12px
}
.prediction-options button{
  min-height:48px;
  padding:10px 12px;
  border:1px solid #ccd9e4;
  border-radius:12px;
  background:#f9fbfd;
  color:#29465e;
  font-weight:900;
  text-align:center
}
.prediction-options button.selected{
  border-color:#175da8;
  background:#eaf3ff;
  color:#174f88;
  box-shadow:inset 0 0 0 1px rgba(23,93,168,.1)
}
.prediction-feedback{
  display:grid;
  gap:3px;
  margin-top:11px;
  padding:11px 12px;
  border-radius:11px;
  border:1px solid #cfe0e8;
  background:#f6fafc;
  color:#4f687b;
  font-size:10px;
  line-height:1.5
}
.prediction-feedback[hidden]{display:none!important}
.prediction-feedback.correct{
  border-color:#add8c8;
  background:#eef9f4;
  color:#356556
}
.prediction-feedback.incorrect{
  border-color:#efd1a7;
  background:#fff8ed;
  color:#76572d
}
.prediction-feedback b{font-size:11px}
.prediction-feedback span{display:block}
.prediction-feedback p{margin:4px 0 0}

body[data-sim-mode="basic"] .lesson-status .check-list{display:none!important}
body[data-sim-mode="basic"] .lesson-status{
  padding:10px 12px;
  background:#f9fbfd
}
body[data-sim-mode="basic"] .lesson-status-head strong::after{
  content:" · 세부 조건은 고급 모드에서 확인";
  color:#8799a8;
  font-size:9px;
  font-weight:600
}

body[data-sim-mode="basic"] .hint-trigger{opacity:.9}
body[data-sim-mode="basic"] .explain{
  font-size:12px;
  padding:12px 14px
}

@media(max-width:760px){
  .beginner-key{display:grid;max-width:560px;margin:0 auto 10px}
  .prediction-card{max-width:560px;padding:13px;margin-bottom:10px}
  .prediction-copy h2{font-size:16px}
  .prediction-options{grid-template-columns:1fr}
  .prediction-options button{min-height:46px}
}

.prediction-feedback-title{
  margin-bottom:3px;color:#175da8;font-size:9px;font-weight:1000;letter-spacing:.04em
}
.prediction-feedback.correct .prediction-feedback-title{color:#08765d}
.prediction-feedback.incorrect .prediction-feedback-title{color:#9a620e}

/* V8 · L2 frame is primary; encapsulated protocol is secondary */
.packet-sprite .frame-title{
  font-size:11px!important;
  font-weight:1000!important;
}
.packet-sprite .frame-sub{
  font-size:8.5px!important;
  font-weight:800!important;
  opacity:.86;
}
.packet-sprite.out .frame-sub{fill:#356fa6}
.packet-sprite.out.flood .frame-sub{fill:#8b5a1b}

.packet-sprite rect{
  width:164px;
  transform:none;
}


/* V9 · completion navigation without scrolling */
.quick-next-bar{
  position:fixed;
  left:50%;
  bottom:14px;
  transform:translateX(-50%);
  z-index:60;
  width:min(760px,calc(100% - 28px));
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:14px;
  padding:11px 12px 11px 15px;
  border:1px solid #a9d8c8;
  border-radius:15px;
  background:rgba(247,252,250,.97);
  box-shadow:0 14px 36px rgba(17,48,66,.18);
  backdrop-filter:blur(10px);
}
.quick-next-bar[hidden]{display:none!important}
.quick-next-copy{min-width:0}
.quick-next-copy small{
  display:block;
  color:#08765d;
  font-size:9px;
  font-weight:1000;
  letter-spacing:.05em
}
.quick-next-copy strong{
  display:block;
  margin-top:2px;
  color:#294a40;
  font-size:11px;
  line-height:1.4
}
.quick-next-btn{
  flex:0 0 auto;
  min-height:42px;
  border:0;
  border-radius:11px;
  padding:10px 16px;
  background:#173b58;
  color:#fff;
  font-weight:1000;
}
body.quick-next-visible{padding-bottom:84px}
body[data-sim-mode="advanced"] .quick-next-bar{display:none!important}

@media(max-width:560px){
  .quick-next-bar{
    bottom:8px;
    width:calc(100% - 16px);
    padding:9px 9px 9px 11px;
    gap:8px
  }
  .quick-next-copy strong{font-size:10px}
  .quick-next-btn{min-height:44px;padding:10px 13px}
  body.quick-next-visible{padding-bottom:78px}
}


/* V11 · prediction first, action second */
body[data-sim-mode="basic"]:not(.prediction-selected) .controls{
  display:none!important;
}
body[data-sim-mode="basic"].prediction-selected .controls{
  animation:primaryActionReveal .18s ease-out both;
}
@keyframes primaryActionReveal{
  from{opacity:0;transform:translateY(-5px)}
  to{opacity:1;transform:translateY(0)}
}


/* V12 · prediction interaction hardening */
.prediction-card{
  position:relative;
  z-index:90;
  pointer-events:auto;
}
.prediction-options,
.prediction-options button{
  position:relative;
  z-index:91;
  pointer-events:auto!important;
  touch-action:manipulation;
}