:root{color-scheme:dark;--bg:#09111e;--panel:#111e30;--panel2:#17263a;--line:#2a3b50;--text:#edf4fd;--muted:#91a3b9;--blue:#4da4f6;--green:#37d0a3;--amber:#f6b85d;--red:#ff7286;--purple:#b68aff}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font:15px/1.5 Inter,system-ui,-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif}button,input,select{font:inherit}button{cursor:pointer}button:disabled{opacity:.45;cursor:not-allowed}.shell{display:flex;min-height:100vh}.sidebar{width:264px;flex-shrink:0;background:#0e1929;border-right:1px solid var(--line);padding:28px 15px;display:flex;flex-direction:column;position:sticky;top:0;height:100vh}.brand{display:flex;align-items:center;gap:11px;padding:0 10px 32px}.brand-icon{width:43px;height:43px;background:linear-gradient(145deg,#207ccf,#38a5ee);border-radius:12px;display:grid;place-items:center;font-weight:900;font-size:20px;color:white;box-shadow:0 5px 24px #1678bc55}.brand-icon span{color:#aaf3f5}.brand 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clamp(20px,4vw,55px);border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:15px}.crumb{font-size:19px;font-weight:750;margin-top:5px}.top-right{display:flex;align-items:center;gap:9px;color:var(--muted)}.status-dot{width:7px;height:7px;border-radius:50%;background:var(--green);box-shadow:0 0 10px var(--green)}.avatar{background:#29435f;color:#d7edff;width:35px;height:35px;border-radius:50%;display:grid;place-items:center;font-size:11px;font-weight:800;margin-left:13px}.content{padding:35px clamp(20px,4vw,55px) 60px;max-width:1560px;margin:auto;min-height:calc(100vh - 145px)}footer{padding:18px 35px;border-top:1px solid var(--line);color:#70839a;font-size:10px;letter-spacing:.7px;text-align:center}.hero{padding:30px 34px;border:1px solid #295a78;border-radius:20px;background:radial-gradient(ellipse at 88% 10%,#174f6e 0,transparent 50%),linear-gradient(120deg,#173250,#102033);margin-bottom:23px}.hero h1{font-size:clamp(24px,3vw,37px);line-height:1.16;margin:8px 0 11px;letter-spacing:-.8px}.hero p{color:#b8d1e5;max-width:670px;margin:0 0 19px}.pill{display:inline-block;border:1px solid #347ba0;border-radius:50px;color:#8cd5ff;padding:4px 10px;font-size:10px;letter-spacing:1px;font-weight:800}.btn{border:1px solid #3673a7;background:#247bc0;color:white;border-radius:9px;padding:10px 15px;font-weight:750;transition:filter .15s}.btn:hover{filter:brightness(1.15)}.btn.secondary{background:#1b2c42;border-color:#3a526c;color:#cbdff2}.btn.green{background:#147e68;border-color:#20b28f}.btn.amber{background:#7b5520;border-color:#b38139}.btn.danger{background:#6b2e3b;border-color:#9d4254}.btn.tiny{padding:6px 10px;font-size:12px}.button-row{display:flex;flex-wrap:wrap;gap:9px;margin-top:16px}.stats{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px;margin-bottom:24px}.stat,.card{border:1px solid var(--line);background:var(--panel);border-radius:15px}.stat{padding:20px}.stat 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7px;font-weight:750}.tag.warn{background:#49351c;border-color:#8a6330;color:#ffd69a}.tag.good{background:#174439;border-color:#256f59;color:#9bf6cf}.flex{display:flex;align-items:center;justify-content:space-between;gap:15px;flex-wrap:wrap}.controls{display:flex;gap:12px;flex-wrap:wrap;align-items:end;margin:14px 0 18px}.field{display:grid;gap:6px}.field label{font-size:11px;font-weight:750;color:#a7bad0;letter-spacing:.3px}.field input,.field select,.answer-input{background:#0b1727;border:1px solid #37516b;border-radius:9px;color:#f2f8ff;padding:11px 12px;min-width:0;outline:none}.field input:focus,.field select:focus,.answer-input:focus{border-color:#62b7ff;box-shadow:0 0 0 2px #318bd633}.field input{width:185px}.field select{min-width:120px}.note{border-left:3px solid var(--blue);background:#132a40;padding:13px 16px;border-radius:5px;color:#bdd5eb;font-size:13px;margin:15px 0}.note.amber{border-color:var(--amber);background:#302717;color:#f4d5a3}.subnet-strip{display:flex;gap:3px;overflow:hidden;border-radius:9px;margin:15px 0 7px}.subnet-segment{flex:1;min-width:2px;height:43px;display:grid;place-items:center;font-size:10px;font-weight:800;color:white}.subnet-segment:nth-child(4n+1){background:#2369a7}.subnet-segment:nth-child(4n+2){background:#16867c}.subnet-segment:nth-child(4n+3){background:#8454a5}.subnet-segment:nth-child(4n){background:#ac7934}.table-wrap{overflow-x:auto;border:1px solid var(--line);border-radius:12px}table{border-collapse:collapse;width:100%;font-size:12px}th{background:#1b2d43;text-align:left;color:#b2c9dc;font-size:10px;text-transform:uppercase;letter-spacing:.5px;padding:13px 11px;white-space:nowrap}td{padding:10px 11px;border-top:1px solid #28394e;white-space:nowrap}tbody tr:nth-child(even){background:#142238}.mono{font-family:ui-monospace,SFMono-Regular,Consolas,monospace}.table-input{background:#0b1727;border:1px solid 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b{color:#79c7fa}.option:hover:not(:disabled){border-color:#62b6ec}.option.chosen{border-color:#60b9f2;background:#1a4562}.option.correct{border-color:#31b992;background:#143d35}.option.wrong{border-color:#f17788;background:#4b2732}.explain{padding:17px;background:#1b3345;border-left:3px solid var(--green);border-radius:8px;margin-top:18px}.explain.trap{border-color:var(--amber);background:#342d21}.score-big{font-size:54px;font-weight:900;letter-spacing:-2px}.center{text-align:center}.chip-row{display:flex;gap:8px;flex-wrap:wrap}.chip{background:#1a2e43;border:1px solid #35506a;padding:7px 11px;border-radius:30px;color:#d2e6f6;font-size:12px}.speed-prompt{font-size:clamp(30px,5vw,54px);font-weight:900;text-align:center;padding:30px 0 12px;letter-spacing:-1px}.speed-input{font-size:24px;text-align:center;width:min(100%,430px);display:block;margin:0 auto}.speed-label{text-align:center;color:var(--muted);font-size:13px}.timer{font:800 21px ui-monospace,monospace;color:var(--amber)}.ref-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.ref-grid .card{margin:0}.ref-table td,.ref-table th{padding:8px}.shortcut{font-size:12px;color:#aac0d2}.divider{height:1px;background:var(--line);margin:18px 0}.hidden{display:none!important}@media(max-width:1000px){.sidebar{width:215px}.stats{grid-template-columns:repeat(2,1fr)}.grid2{grid-template-columns:1fr}}@media(max-width:700px){.shell{display:block}.sidebar{position:relative;height:auto;width:100%;padding:12px}.brand{padding:4px 4px 10px}.sidebar-label,.side-bottom{display:none}nav{display:flex;overflow-x:auto;gap:5px}nav button{flex:0 0 auto;font-size:11px;padding:9px 10px}nav button span{width:17px}.topbar{padding:15px 18px}.top-right .small,.eyebrow{display:none}.content{padding:20px 12px 50px}.hero{padding:22px}.stats{gap:8px}.stat{padding:14px}.stat 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