.book-main {
    margin-bottom: 10px;
}

.read-btn:hover {
    background-color: #0848ad;
}

.pdf-tabs .pdf-tab-header {
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 20px;
    padding: 0;
    margin: 0 0 12px 0;
    position: relative;
}

    /* tab nút icon vuông */
    .pdf-tabs .pdf-tab-header .tab-item {
        width: 60px;
        height: 60px;
        background: var(--background-light);
        border: 1px solid var(--border-color);
        border-radius: 10px;
        display: flex;
        justify-content: center;
        align-items: center;
        font-size: 24px;
        color: var(--text-mute);
        cursor: pointer;
        transition: all 0.25s ease;
    }

        .pdf-tabs .pdf-tab-header .tab-item:hover {
            background: var(--hover-bg);
        }

        .pdf-tabs .pdf-tab-header .tab-item.active {
            background: var(--primary-color);
            color: white;
            border-color: var(--primary-dark);
        }

.flipbook-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.88);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 99999;
}

/* Popup bên trong */
.flipbook-popup {
    position: relative;
    width: 90%;
    height: 90%;
    background: #000;
    border-radius: 10px;
    box-shadow: 0 0 25px rgba(0,0,0,0.4);
    overflow: hidden;
}

/* nút đóng */
.close-popup {
    position: absolute;
    top: 12px;
    right: 12px;
    background: rgba(0,0,0,0.65);
    border: none;
    color: white;
    font-size: 22px;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    cursor: pointer;
    z-index: 1000;
}

    .close-popup:hover {
        background: rgba(0,0,0,0.85);
    }

/* iframe fullscreen */
.flipbook-fullscreen-iframe {
    width: 100%;
    height: 100%;
    border: none;
}

/* ==== ZOOM BUTTON ==== */
.pdf-tabs .tab-zoom {
    position: absolute;
    right: 0;
    top: 0;
}

.pdf-tabs .zoom-btn {
    width: 42px;
    height: 42px;
    border-radius: 10px;
    border: 1px solid var(--border-color);
    background: var(--primary-color);
    color: white;
    font-size: 18px;
    cursor: pointer;
    transition: background 0.25s ease;
}

    .pdf-tabs .zoom-btn:hover {
        background: var(--primary-dark);
    }

@media (max-width: 1000px) {

    .tab-content, .book-main, .book-tabs {
        max-height: 700px;
    }
}