header, main {
    padding: 30px;
}
header {
    width: 50vw;
    margin: auto;
}
main {
    display: grid;
    gap: 15px;
    grid-template-columns: repeat(3, 1fr);
}
main section {
    border: 3px dashed #444864;
    padding: 30px;
    border-radius: 5px;
}
/* md */ 
@media (max-width: 768px) {
    main {
        grid-template-columns: repeat(1, 1fr);
    }
}
@media (prefers-color-scheme: light) {
    main section {
        border-color: #ccb7ec;
    }
}