body {
    background-color: #000;
    color: #00ffcc;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    text-align: center;
    padding-top: 50px;
}
.container {
    border: 2px solid #00ffcc;
    display: inline-block;
    padding: 30px;
    border-radius: 15px;
    box-shadow: 0 0 20px #00ffcc;
}
#result {
    margin-top: 20px;
    font-size: 1.5rem;
    min-height: 50px;
}
button {
    background: transparent;
    color: #00ffcc;
    border: 1px solid #00ffcc;
    padding: 10px 20px;
    cursor: pointer;
    border-radius: 5px;
}
button:hover {
    background: #00ffcc;
    color: #000;
}