body { font-family: sans-serif; background: #f8f8f8; margin: 0; font-size: 17px; }
    .tabs { display: flex; background: #333; }
    .tab { flex: 1; padding: 15px; color: white; text-align: center; cursor: pointer; }
    .tab.active { background: #555; }
    .content { display: none; padding: 20px; }
    .content.active { display: block; }