body {
    font-family: Arial, sans-serif;
    text-align: center;
    background: #222;
    padding: 20px;
}

.back-link {
    position: absolute;
    top: 20px;
    left: 20px;
    color: #fff;
    text-decoration: none;
    font-weight: 500;
    padding: 8px 12px;
    border-radius: 6px;
    background: rgba(255,255,255,0.1);
}

.back-link:hover {
    background: rgba(255,255,255,0.2);
}

div {
    text-align: center;
    background: white;
    padding: 30px;
    border-radius: 10px;
    width: 90%;
    max-width: 600px;
    margin: auto;
}

input {
    font-size: 24px;
    width: 80px;
    padding: 5px;
    text-align: center;
}

button {
    font-size: 18px;
    padding: 8px 20px;
    margin: 5px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
}

#startBtn {
    background: green;
    color: white;
}

#resetBtn {
    background: red;
    color: white;
}

#display {
    font-size: 60px;
    font-family: monospace;
    margin: 20px 0;
}