body {
    max-width: 1000px;
}

.gallery {
    column-count: 2;
    column-gap: 5px;
}

.gallery figure {
    margin: 0;
    margin-bottom: 5px;
    break-inside: avoid;
    position: relative;
    display: block;
}

.gallery figure img {
    width: 100%;
    height: auto;
    display: block;
    border-radius: 5px;
}

.gallery figure figcaption {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    border-radius: 5px;
    align-items: center;
    justify-content: center;
    background: rgba(0, 0, 0, 0.5);
    color: white;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.gallery figure:hover figcaption {
    opacity: 1;
}

@media (max-width: 780px) {
    .gallery {
        column-count: 1;
    }
}

a,
a:link,
a:visited {
    color: #0000EE;
    text-decoration: none;
}

details {
    margin: 0;
    padding: 0.5em;
    border: 1px dashed #D0D0D0;
    border-radius: 5px;
}

details>summary {
    cursor: pointer;
}

details> :not(summary) {
    margin-left: 1.3em;
    padding-right: 1em;
}

details>summary>* {
    margin: 0;
}

details>summary::marker,
details>summary::-webkit-details-marker {
    content: "➡️ ";
}

details[open]>summary::marker,
details[open]>summary::-webkit-details-marker {
    content: "⬇️ ";
}