body { 
    font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, sans-serif; 
    background-color: #f4f6f9; 
    margin: 0; 
    padding: 20px 10px; 
    color: #333; 
}
.container { 
    width: 100%;
    max-width: 550px; 
    background: #fff; 
    margin: 10px auto; 
    padding: 24px; 
    border-radius: 8px; 
    box-shadow: 0 4px 12px rgba(0,0,0,0.06); 
    box-sizing: border-box;
}
h2, h3 { margin-top: 0; color: #2c3e50; padding-bottom: 8px; }
h2 { border-bottom: 2px solid #ecf0f1; font-size: 1.4rem; }
.header-meta { 
    display: flex; 
    justify-content: space-between; 
    align-items: center; 
    background: #eef2f7; 
    padding: 10px 12px; 
    border-radius: 5px; 
    margin-bottom: 20px; 
    font-size: 0.85rem; 
}
.logout-btn { color: #c0392b; font-weight: bold; text-decoration: none; }
.os-warning { 
    color: #d32f2f; 
    font-weight: bold; 
    font-size: 0.95rem; 
    background-color: #ffebee; 
    padding: 10px; 
    border-left: 5px solid #d32f2f; 
    margin-bottom: 20px; 
    border-radius: 4px; 
    text-align: center; 
}
.form-group { margin-bottom: 16px; }
label { display: block; margin-bottom: 5px; font-weight: 600; color: #34495e; font-size: 0.9rem; }
input[type="text"], input[type="email"], input[type="password"], select { 
    width: 100%; 
    padding: 11px 10px; 
    border: 1px solid #ccc; 
    border-radius: 4px; 
    box-sizing: border-box; 
    font-size: 1rem;
    -webkit-appearance: none;
}
.checkbox-group { display: flex; align-items: center; gap: 8px; margin: 15px 0; }
.checkbox-group label { margin-bottom: 0; }
button { 
    width: 100%; 
    background-color: #3498db; 
    color: white; 
    border: none; 
    padding: 13px; 
    font-size: 1.05rem; 
    font-weight: bold; 
    border-radius: 4px; 
    cursor: pointer; 
    transition: background 0.2s; 
}
button.success-btn { background-color: #2ecc71; }
button.success-btn:hover { background-color: #27ae60; }
.alert { 
    padding: 12px; 
    border-radius: 4px; 
    margin-bottom: 20px; 
    font-weight: 500; 
    font-size: 0.95rem;
    word-break: break-all;
}
.success { background-color: #d4edda; color: #155724; border: 1px solid #c3e6cb; }
.error { background-color: #f8d7da; color: #721c24; border: 1px solid #f5c6cb; }
.admin-section { background: #fcfcfc; border: 1px dashed #bdc3c7; padding: 16px; border-radius: 6px; margin-top: 25px; }
.toggle-link { text-align: center; margin-top: 15px; font-size: 0.9rem; }
.toggle-link a { color: #3498db; text-decoration: none; font-weight: bold; }

@media (max-width: 480px) {
    body { padding: 10px 4px; }
    .container { padding: 16px; margin: 5px auto; }
    h2 { font-size: 1.25rem; }
    .header-meta { flex-direction: column; gap: 6px; text-align: center; }
    button { padding: 11px; font-size: 0.95rem; }
}