.alert{padding:14px 18px;border-radius:8px;font-size:16px;margin-bottom:16px;border:1px solid transparent;position:relative;transition:opacity .2s}.alert-danger{background:#f8d7da;color:#842029;border-color:#f5c2c7}.alert-success{background:#d1e7dd;color:#0f5132;border-color:#badbcc}.alert-warning{background:#fff3cd;color:#664d03;border-color:#ffecb5}.alert-info{background:#cff4fc;color:#055160;border-color:#b6effb}.btn-close{background:none;border:none;font-size:20px;color:inherit;opacity:.7;cursor:pointer;position:absolute;top:8px;right:12px;line-height:1}.btn-close:hover{opacity:1}:root{--bg: #f6f8fb;--card: #ffffff;--muted: #6b7280;--accent: #2563eb;--accent-2: #06b6d4}body{font-family:Inter,ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Helvetica Neue,Arial;background:var(--bg);margin:0;color:#111827}.app-root{min-height:100vh;display:flex;flex-direction:column}.app-header{display:flex;justify-content:center;align-items:center;padding:20px 40px;background:linear-gradient(90deg,#fff,#f8fafc);box-shadow:0 1px 4px #1018280a;position:relative}.header-icon{width:64px;height:64px;background:linear-gradient(180deg,#fff,#f3f4f6);border-radius:16px;display:flex;align-items:center;justify-content:center;box-shadow:0 6px 20px #6366f11f}.app-header .header-icon{position:absolute;left:40px}.app-title{margin:0;font-size:32px;font-weight:700}.app-subtitle{margin:6px 0 0;color:var(--muted);font-size:14px}.lang-controls{position:absolute;right:40px}.app-title{margin:0;font-size:20px}.lang-controls .btn{margin-left:8px}.container{display:flex;gap:20px;padding:24px;max-width:1100px;margin:20px auto;width:100%}.hero-card{width:100%;max-width:820px;margin:24px auto;padding:34px;border-radius:20px;background:linear-gradient(180deg,#fff,#fbfdff);box-shadow:0 12px 30px #0206170f}.hero-form .field{margin-bottom:16px}.input-large{width:100%;padding:14px 18px;border-radius:12px;border:1px solid #eef2ff;box-shadow:inset 0 1px #fff9;font-size:16px}.btn.primary.large{background:linear-gradient(90deg,#5b21b6,#6d28d9);color:#fff;padding:16px 20px;border-radius:14px;font-weight:700;font-size:16px;width:100%}.sidebar{width:320px}.content{flex:1}.card{background:var(--card);padding:16px;border-radius:10px;box-shadow:0 4px 12px #1118270a;margin-bottom:16px}.btn{background:transparent;border:1px solid #d1d5db;padding:8px 12px;border-radius:8px;cursor:pointer}.btn.primary{background:var(--accent);color:#fff;border-color:transparent}.btn.full{width:100%;display:block}.btn:hover{opacity:.95}.select{width:100%;padding:8px;border-radius:8px;border:1px solid #e5e7eb}.label{display:block;margin-top:12px;margin-bottom:6px;color:var(--muted)}.meta{color:var(--muted);font-size:13px}.lesson h2{margin-top:0}.placeholder{color:var(--muted);padding:40px;text-align:center}.footer{padding:12px;text-align:center;color:var(--muted);font-size:13px}.ai-text{white-space:pre-wrap;background:linear-gradient(180deg,#f8fafc,#fff);padding:12px;border-radius:8px}.menu-bar{display:inline-flex;gap:8px;padding:6px;border-radius:14px;background:#f8fafc;border:1px solid #eef2ff}.menu-icon-btn{width:38px;height:38px;border-radius:12px;border:1px solid transparent;background:transparent;color:#111827;display:inline-flex;align-items:center;justify-content:center;cursor:pointer}.menu-icon-btn:hover{background:#fff;border-color:#eef2ff}.menu-icon-btn.active{background:#111827;color:#fff}.badge{display:inline-flex;align-items:center;padding:4px 10px;border-radius:999px;font-size:12px;border:1px solid transparent}.badge-success{background:#d1e7dd;color:#0f5132;border-color:#badbcc}.badge-danger{background:#f8d7da;color:#842029;border-color:#f5c2c7}.badge-info{background:#cff4fc;color:#055160;border-color:#b6effb}details.card>summary.summary-row{cursor:pointer;list-style:none}details.card>summary.summary-row::-webkit-details-marker{display:none}.muted{color:var(--muted);font-size:13px}@media (max-width:900px){.container{flex-direction:column;padding:12px}.sidebar{width:100%}}