#app{font-family:Arial,sans-serif;text-align:center;margin-top:50px}.timer{font-size:4rem;font-weight:700;margin:20px 0}button{font-size:1.2rem;padding:10px 20px;border-radius:5px;border:none;background-color:#4caf50;color:#fff;cursor:pointer}button:disabled{background-color:#ccc;cursor:not-allowed}