Assessment wanted for Media Queries and Responsive Web Design

MDN Learn
,
#1

Hello, I would like comments on how I did for this assessment.
Test your skills: Responsive web design and media queries

CSS below:

@media screen and (min-width: 45em) {
    header{
        display: flex;
        justify-content: space-between;
        align-items: center;
    }
    body {
        margin: 0;
    }
    header .title, nav a {
        padding: 0.9rem;
    }
    nav ul {
        display: flex;
        align-items: center;
    }
    nav a {
        border-top: none;
    }

.cards {
    display: grid;
    gap: 10px;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
}
main {
    margin-top: 1rem;
    display: grid;
    gap: 10px;
    grid-template-columns: 3fr 1fr;
}
}

@media screen and (min-width: 70em) {
.cards {
    display: grid;
    gap: 10px;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
}
}