@media (min-width: 40em) {
    main {
        margin: 4em;
    }
}

details.program:first-child {
    border-top: 1px solid black;
}

details.program {
    position: relative;
    width: 100%;
    border-bottom: 1px solid black;
}

details.program > summary {
    list-style: none;
}
details.program > summary::-webkit-details-marker {
    display: none;
}

details.program > summary:after {
    position: absolute;
    right: 1em;
    content: '∨';
}

details.program[open] > summary:after {
    content: '∧';
    bottom: 0;
}