body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #f0f0f0;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Arial', sans-serif;
}

.grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 10px;
    width: 400px;
    height: 400px;
}

.tile {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    grid-template-rows: repeat(2, 1fr);
    gap: 5px;
    background: #888;
    padding: 5px;
    box-sizing: border-box;
}

.subtile {
    background: #aaa;
    display: flex;
    justify-content: center;
    align-items: center;