* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html, body {
    height: 100%;
    font-family: -apple-system, "Hiragino Sans", "Yu Gothic", sans-serif;
}

body {
    display: flex;
    flex-direction: column;
    height: 100vh;
    overflow: hidden;
}

.site-header {
    text-align: center;
    padding: 0.5rem 1rem 0.3rem;
    flex-shrink: 0;
    position: relative;
}

.site-header h1 {
    font-size: clamp(1rem, 2.6vw, 1.5rem);
    letter-spacing: 0.15em;
    font-weight: 500;
}

.site-header .subtitle {
    font-size: clamp(0.65rem, 1.6vw, 0.85rem);
    opacity: 0.7;
    letter-spacing: 0.1em;
    margin-top: 0.2rem;
}

.catalog-wrapper {
    flex: 1 1 auto;
    min-height: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem;
    overflow: hidden;
}

.book { display: block; }

.book .page {
    background: #fff;
    overflow: hidden;
}

.book .page img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
    user-select: none;
    -webkit-user-drag: none;
}

.controls {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1rem;
    padding: 0.4rem;
    flex-shrink: 0;
}

.ctrl-btn {
    background: transparent;
    padding: 0.4rem 1rem;
    font-size: 0.9rem;
    cursor: pointer;
    border-radius: 4px;
    font-family: inherit;
    transition: background 0.2s, border-color 0.2s, color 0.2s;
    border: 1px solid currentColor;
}

.page-indicator {
    font-size: 0.9rem;
    min-width: 5rem;
    text-align: center;
}

.site-footer {
    text-align: center;
    padding: 0.3rem;
    font-size: 0.7rem;
    flex-shrink: 0;
}

.back-link {
    position: fixed;
    top: 0.6rem;
    left: 0.9rem;
    z-index: 100;
    text-decoration: none;
    font-size: 0.72rem;
    padding: 0.3rem 0.7rem;
    border-radius: 3px;
    opacity: 0.7;
    transition: opacity 0.2s;
    border: 1px solid currentColor;
    background: rgba(0, 0, 0, 0.15);
}

.back-link:hover {
    opacity: 1;
}

@media (max-width: 767px) {
    .site-header { padding: 0.4rem 1rem 0.2rem; }
    .ctrl-btn { padding: 0.35rem 0.8rem; font-size: 0.8rem; }
    .back-link { font-size: 0.68rem; top: 0.4rem; left: 0.5rem; }
}