body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 20px;
    background: #8b5a2b;
    background-image:
        linear-gradient(90deg, rgba(255,275,255,0.1) 1px, transparent 1px),
        linear-gradient(0deg, rgba(0,0,0,0.1) 1px, transparent 1px);
    background-size: 30px 30px;
    display: flex;
    flex-direction: column;
    align-items: center;
}
h1 {
    color: #fff;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.7);
    margin-bottom: 15px;
}
table {
    border-collapse: collapse;
    background: #8b5a2b;
    border: 8px solid #5a3714;
    box-shadow: 0 4px 6px rgba(0,0,0,0.3);
}
td {
    width: 50px;
    height: 50px;
    border: 1px solid #5a3714;
    background: url('https://www.publicdomainpictures.net/pictures/30000/nahled/wood-texture-3.jpg') center/cover;
}
td:nth-child(3), td:nth-child(6) {
    border-right: 3px solid #5a3714;
}
tr:nth-child(3) td, tr:nth-child(6) td {
    border-bottom: 3px solid #5a3714;
}
input {
    width: 100%;
    height: 100%;
    border: none;
    text-align: center;
    font-size: 20px;
    background: transparent;
    color: #fff;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.8);
}
input.error {
    color: red;
}
input:disabled {
    color: yellow;
    font-weight: bold;
}
.buttons {
    margin-top: 15px;
}
button {
    margin: 0 5px;
    padding: 8px 16px;
    font-size: 16px;
    border: none;
    background: #5a3714;
    color: #fff;
    cursor: pointer;
    box-shadow: 0 2px 4px rgba(0,0,0,0.3);
}
button:hover {
    background: #7a4e20;
}