* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.gridBox {
    display: grid;
    grid-template-columns: repeat(12, 1fr);
    background-color: aquamarine;
    width: 90%;
    margin: 0 auto;
    gap: 16px;
    grid-auto-rows: minmax(100px, auto);
    background-image:
        repeating-linear-gradient(90deg,
            pink 0px,
            pink calc((100% - ((12 - 1) * 16px)) / 12),
            transparent calc((100% - (12 * 16px)) / 12),
            transparent calc((100% - ((12 - 1) * 16px)) / 12 + 16px));
}

h2 {
    grid-column: span 3;
    background-color: rgb(120, 91, 250);
}

h3 {
    grid-row: 2;
}