:root{--bg: #f7f8fa;--surface: #ffffff;--surface-alt: #eef1f4;--text: #1f2733;--text-muted: #5b6472;--border: #dde2e8;--primary: #3d6b8a;--primary-hover: #2f5670;--primary-contrast: #ffffff;--accent: #3f8f68;--accent-bg: #e6f2eb;--danger: #b3492f;--danger-bg: #f6e6e1;--warning: #a6721f;--warning-bg: #f5ead4;--shadow: 0 1px 3px rgba(20, 24, 29, .08), 0 1px 2px rgba(20, 24, 29, .06);--radius: 10px;--chart-series-1: #2a78d6;--chart-series-2: #eb6834;--chart-error: #d03b3b}:root[data-theme=dark]{--bg: #14181d;--surface: #1c2128;--surface-alt: #242a32;--text: #e6e9ed;--text-muted: #9aa4b2;--border: #2e3540;--primary: #6fa8c9;--primary-hover: #8ec0dd;--primary-contrast: #10171d;--accent: #6bbf98;--accent-bg: #1c2e26;--danger: #d97a5f;--danger-bg: #33211c;--warning: #dba648;--warning-bg: #332a17;--shadow: 0 1px 3px rgba(0, 0, 0, .35), 0 1px 2px rgba(0, 0, 0, .3);--chart-series-1: #3987e5;--chart-series-2: #d95926;--chart-error: #d03b3b}*{box-sizing:border-box}html,body{margin:0;padding:0}body{background:var(--bg);color:var(--text);font-family:Segoe UI,system-ui,-apple-system,sans-serif;min-height:100vh}#app{display:flex;flex-direction:column;min-height:100vh}.topbar{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:14px 24px;background:var(--surface);border-bottom:1px solid var(--border)}.topbar__brand{font-size:18px;font-weight:600;color:var(--text)}.topbar__controls{display:flex;align-items:center;gap:10px}main{flex:1;padding:32px 24px 60px;max-width:920px;width:100%;margin:0 auto}.centered-panel{max-width:420px;margin:10vh auto 0;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow);padding:32px;text-align:center}h1{font-size:24px;margin:0 0 6px}h2{font-size:19px;margin:0 0 16px}p.subtitle{color:var(--text-muted);margin:0 0 24px}button{font:inherit;cursor:pointer;border-radius:8px;border:1px solid var(--border);background:var(--surface-alt);color:var(--text);padding:9px 16px}button:hover{filter:brightness(.97)}:root[data-theme=dark] button:hover{filter:brightness(1.15)}button.primary{background:var(--primary);border-color:var(--primary);color:var(--primary-contrast);font-weight:600}button.danger{background:transparent;border-color:var(--danger);color:var(--danger)}button.icon{padding:8px 10px;font-size:15px}input[type=text],input[type=email]{font:inherit;font-size:14px;padding:11px 14px;border-radius:8px;border:1px solid var(--border);background:var(--bg);color:var(--text);width:100%;transition:border-color .15s ease}input[type=text]:focus,input[type=email]:focus{outline:none;border-color:var(--primary)}input[type=text]::placeholder,input[type=email]::placeholder{color:var(--text-muted)}.field{display:flex;flex-direction:column;gap:6px;text-align:left}.field label{font-size:13px;font-weight:600;color:var(--text-muted)}.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow);padding:20px}.stack{display:flex;flex-direction:column;gap:16px}.row-between{display:flex;align-items:center;justify-content:space-between;gap:12px}.section-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:16px}.section{display:flex;flex-direction:column;gap:14px}.section+.section{margin-top:12px;padding-top:28px;border-top:1px solid var(--border)}.class-list{display:flex;flex-direction:column;gap:12px}.class-row{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:12px;padding:14px 18px;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow)}.class-row__info{flex:1 1 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img{background:#fff;padding:8px;border-radius:8px}.join-code{font-size:15px;letter-spacing:2px;font-weight:700;font-variant-numeric:tabular-nums}table{width:100%;border-collapse:collapse}th,td{text-align:left;padding:10px 12px;border-bottom:1px solid var(--border);font-size:14px}th{color:var(--text-muted);font-weight:600;font-size:12px;text-transform:uppercase;letter-spacing:.03em}.empty-state{color:var(--text-muted);text-align:center;padding:40px 0}.lang-switch{display:flex;border:1px solid var(--border);border-radius:8px;overflow:hidden}.lang-switch button{border:none;border-radius:0;background:var(--surface);padding:7px 10px;font-size:12px}.lang-switch button.active{background:var(--primary);color:var(--primary-contrast)}.join-page{max-width:420px;margin:12vh auto 0;text-align:center}.join-page .join-code{font-size:40px;margin:20px 0}.stats-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:14px}.stat-tile{background:var(--surface);border:1px solid 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