:root{--bg:#0f172a;--card:#111827;--text:#e5e7eb;--muted:#9ca3af;--accent:#22c55e;--danger:#ef4444}
*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font-family:system-ui,Segoe UI,Roboto,Arial,sans-serif}
.container{max-width:980px;margin:0 auto;padding:16px}
.navbar{background:#0b1220;border-bottom:1px solid #1f2937}
.navbar .brand{color:#fff;text-decoration:none;font-weight:700}
nav a{color:#e5e7eb;text-decoration:none;margin-left:12px}
.btn{display:inline-block;padding:8px 12px;border:1px solid #334155;border-radius:8px;background:#1f2937;color:#e5e7eb;text-decoration:none}
.btn.primary{background:var(--accent);border-color:transparent;color:#052e16}
.alert{padding:10px 12px;border-radius:8px;margin:8px 0}
.alert.error{background:#2b0a0a;color:#fecaca;border:1px solid #7f1d1d}
.auth form{display:grid;gap:10px;max-width:360px}
.auth input[type=email],.auth input[type=password],.auth input[type=text]{width:100%;padding:10px;border-radius:8px;border:1px solid #334155;background:#0b1220;color:#e5e7eb}
.courses{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:12px}
.course-card{display:block;padding:16px;border-radius:12px;background:var(--card);text-decoration:none;color:var(--text);border:1px solid #1f2937;transition:.2s}
.course-card:hover{transform:translateY(-2px);border-color:#334155}
.course-emoji{font-size:32px}
.course-title{font-weight:700;margin-top:8px}
.course-desc{color:var(--muted);font-size:14px}
.unit{margin:24px 0}
.lessons{display:flex;gap:10px;flex-wrap:wrap}
.lesson-card{display:inline-flex;gap:8px;align-items:center;padding:10px 12px;border-radius:10px;background:#0b1220;border:1px solid #1f2937;color:#e5e7eb;text-decoration:none}
.lesson-pos{opacity:.7}
.lesson{max-width:720px}
.exercise{padding:16px;background:var(--card);border-radius:12px;border:1px solid #1f2937}
.exercise-prompt{font-size:18px;margin-bottom:12px}
.choices{display:grid;gap:8px}
.choice{display:flex;align-items:center;gap:8px;padding:8px;border-radius:8px;background:#0b1220;border:1px solid #1f2937}
.result{margin-top:12px;padding:10px;border-radius:8px}
.result.ok{background:#052e16;border:1px solid #166534}
.result.bad{background:#3f0b0b;border:1px solid #7f1d1d}