style.css

*, *::before, *::after {
    box-sizing: border-box;
    font-family: Arial;
}

body {
    background-color: #333;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    font-size: 7.5vmin;
}

#game-board {
    --grid-size: 4;
    --cell-size: 20vmin;
    --cell-gap: 2vmin;
    display: grid;
    grid-template-columns: repeat(var(--grid-size), var(--cell-size));
    grid-template-rows: repeat(var(--grid-size), var(--cell-size));
    background-color: #CCC;
    gap: var(--cell-gap);
    border-radius: 1vmin;
    padding: var(--cell-gap);
    position: relative;
}

.cell {
    background-color: #AAA;
    border-radius: 1vmin;
}

.tile {
    position: absolute;
    display: flex;
    justify-content: center;
    align-items: center;
    width: var(--cell-size);
    height: var(--cell-size);
    background-color: red;
    border-radius: 1vmin;
    top: calc(var(--y) * (var(--cell-size) + var(--cell-gap)) + var(--cell-gap));
    left: calc(var(--x) * (var(--cell-size) + var(--cell-gap)) + var(--cell-gap));
    font-weight: bold;
    background-color: hsl(200, 50%, var(--background-lightness));
    color: hsl(200, 25%, var(--text-lightness));
    animation: show 200ms ease-in-out; /* Added animation name */
    transition: 100ms ease-in-out;
}

/* Modal Styles */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
}

/* Modal styles */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.4);
    z-index: 1;
}

.modal-content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: #fefefe;
    padding: 20px;
    border: 1px solid #888;
    border-radius: 5px;
    text-align: center;
}

.close-modal {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
}

.close-modal:hover {
    color: black;
}