body {
    background: #f8f7f6;
    margin: 0;
    padding: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    overflow: hidden;
}

#main-image {
    width: 100vw;
    object-fit: cover;
    object-position: 0 -50px;
    display: block;
    background: #f8f7f6;
    box-shadow: 0 0 10px rgba(0,0,0,0.05);
}

#fullscreenBtn {
    margin: 1rem 0;
    font-size: 1.2rem;
}

a {
    display: block;
    margin-top: 1rem;
    font-size: 1.2rem;
}

.fullscreen-iframe {
    width: 100vw;
    height: calc(100vh - 20px - env(safe-area-inset-bottom));
    border: none;
}

@media (min-width: 768px) {
    .fullscreen-iframe {
        width: 390px;
        margin: 0 auto; /* 中央揃え */
    }
}