style.scss

body{
    width: 100%;
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    background-color: goldenrod;
}
#puzzle { 
    display: flex; 
    flex-wrap: wrap; 
    width: 300px; 
    height: 300px; 
    margin: 20px auto; 
    border: 1px solid #000;
    box-shadow: 3px 5px 2px 5px rgba(0,0,0,0.5);

    .piece { 
        width: 100px; 
        height: 100px; 
        border: 1px solid #000; 
        box-sizing: border-box; 
        cursor: pointer; 
        font-size: 32px;
        display: flex;
        justify-content: center;
        align-items: center;
        transition: background-color 0.3s;

        &:hover {
            background-color: #f0f0f0;
        }

        &.empty {
            background-color: #f0f0f0;
        }
    }
}

button {
    display: block;
    margin: 0 auto;
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
    border: 1px solid #000;
    background-color:transparent;
    color: #fff;
    border-radius: 5px;
    transition: background-color 0.3s;

    &:hover {
        background-color: #fff;
        color: #000;
    }
}