body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    overflow: hidden;
    font-family: Arial, sans-serif;
}

.background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    display: flex;
}

.bg-image {
    position: absolute;
    width: 100%;
    height: 100%;
    background-size: cover;
    background-position: center;
    animation: fade 15s infinite;
    opacity: 0;
}

.bg-image:nth-child(1) {
    background-image: url('background/001.png');
    animation-delay: 0s;
}

.bg-image:nth-child(2) {
    background-image: url('background/002.png');
    animation-delay: 5s;
}

.bg-image:nth-child(3) {
    background-image: url('background/003.png');
    animation-delay: 10s;
}

@keyframes fade {
    0%, 100% { opacity: 0; }
    25%, 75% { opacity: 1; }
}

.content {
    position: relative;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
}

.menu {
    position: absolute;
    top: 20px;
    right: 20px;
    display: flex;
    flex-direction: column;
    align-items: flex-end;
}

.hamburger {
    width: 30px;
    height: 25px;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    cursor: pointer;
}

.line {
    width: 100%;
    height: 3px;
    background-color: white;
}

.menu-content {
    display: none;
    flex-direction: column;
    margin-top: 10px;
}

.menu-content a {
    color: white;
    text-decoration: none;
    margin-bottom: 5px;
}

.main-container {
    width: 95vw;
    height: auto;
    max-width: 1024px;
    border: 2px solid white;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: flex-start;
    padding: 10px;
    box-sizing: border-box;
    margin-top: 80px;
}

.illust-gallery {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: flex-start;
    align-items: flex-start;
}

.illust-link {
    width: 150px;
    height: auto;
    cursor: pointer;
}

.illust-link img {
    width: 100%;
    height: auto;
    transition: transform 0.3s;
}

.illust-link:hover img {
    transform: scale(1.1);
}

.modal {
    display: none;
    position: fixed;
    z-index: 1;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0,0,0,0.9);
}

.modal-content {
    margin: auto;
    display: block;
    width: 80%;
    max-width: 700px;
}

.close {
    position: absolute;
    top: 15px;
    right: 35px;
    color: #f1f1f1;
    font-size: 40px;
    font-weight: bold;
    transition: 0.3s;
}

.close:hover,
.close:focus {
    color: #bbb;
    text-decoration: none;
    cursor: pointer;
}

.free-space {
    flex: 1;
    color: white;
    font-size: 12px;
    width: 100%;
    height: 20vw;
    border: 2px solid white;
    margin-top: 10px;
    background: rgba(0, 0, 0, 0.5); /* 黒の半透明背景 */
    display: flex;
    align-items: flex-start;  /* 左寄せ */
    padding: 10px;
    box-sizing: border-box;
}

.icon-link {
    margin-left: 10px;
}

.icon-link img {
    width: 50px;
    height: auto;
}