body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 20px;
}

nav {
    margin-bottom: 20px;
}

.tab-button {
    padding: 10px 15px;
    cursor: pointer;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.bingo-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
}

.bingo-square {
    position: relative;
    border: 1px solid #ccc;
    aspect-ratio: 1 / 1;
    padding: 10px;
    text-align: center;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
}

.bingo-square.completed {
    opacity: 0.45;
    filter: grayscale(100%);
    position: relative;
}

.bingo-square.completed::after {
    content: "✓";
    position: absolute;
    top: 8px;
    right: 10px;
    font-size: 28px;
    font-weight: bold;
}

.toast {
    display: none;
    position: fixed;
    bottom: 20px;
    left: 20px;
    right: 20px;
    padding: 12px 16px;
    background: #222;
    color: white;
    border-radius: 8px;
    text-align: center;
}