:root {
    --bg-color: #333;
    --panel-bg: rgba(0, 0, 0, 0.8);
    --panel-text: #fff;
    --accent-color: #ccc;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    height: 100vh;
    padding: 20px;
    /* Add some spacing */
    cursor: default;
}

/* Container for the book */
.viewer-container {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    width: 100%;
    overflow: hidden;
    padding: 20px;
    cursor: default;
}

/* NUCLEAR OPTION: When zoomed, strictly disable interaction with the book */
.viewer-container.zoomed-mode {
    /* Allow regular flexing/centering */
    display: block;
    /* Switch to block to allow scroll */
    overflow: auto;
    /* Ensure scrollbars work if needed (hidden by JS mainly) */
}

/* Ensure book centers and handles overflow safely */
.viewer-container.zoomed-mode .flip-book {
    margin: auto;
    /* Magic centering fix for overflow */
    pointer-events: none !important;
}

.viewer-container.zoomed-mode .flip-book * {
    pointer-events: none !important;
}

/* Pan Overlay */
#pan-overlay {
    position: absolute;
    top: 0;
    left: 0;
    /* Dimensions set by JS */
    z-index: 2000;
    /* Above EVERYTHING in container */
    display: none;
    /* Hidden by default */
    cursor: grab;
}

#pan-overlay.dragging {
    cursor: grabbing;
}

.loader {
    position: absolute;
    color: white;
    font-size: 1.5rem;
    z-index: 1000;
}

/* The Flipbook element */
.flip-book {
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.5);
    display: none;
    /* Hidden until loaded */
    background-size: cover;
    flex-shrink: 0;
}

/* Individual Pages (Canvas wrappers) */
.page {
    background-color: white;
    box-shadow: inset 0 0 20px rgba(0, 0, 0, 0.1);
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    transform-style: preserve-3d;
}

.page canvas {
    display: block;
    width: 100%;
    height: 100%;
    vertical-align: top;
}

/* Control Panel */
.control-panel {
    height: 60px;
    background-color: var(--panel-bg);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
    padding: 0 20px;
    backdrop-filter: blur(5px);
    width: 100%;
    /* Mobile Stability Fixes */
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 9999;
    transform: translateZ(0);
    /* Force GPU Layer */
    -webkit-transform: translateZ(0);
}

.control-panel button,
.control-panel a#btnDownload {
    background: none;
    border: none;
    color: var(--panel-text);
    font-size: 1.2rem;
    cursor: pointer;
    padding: 8px;
    border-radius: 5px;
    transition: background 0.2s, color 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
}

.control-panel button:hover,
.control-panel a#btnDownload:hover {
    background: rgba(255, 255, 255, 0.1);
    color: var(--accent-color);
}

.page-info {
    display: flex;
    /* Desktop default */
    align-items: center;
    gap: 5px;
    color: var(--panel-text);
    font-weight: bold;
}

.page-info input {
    width: 50px;
    text-align: center;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid #555;
    color: white;
    padding: 5px;
    border-radius: 4px;
}

/* Main Layout */
.main-layout {
    display: flex;
    flex-direction: row;
    height: 100vh;
    overflow: hidden;
    width: 100%;
    padding-bottom: 60px;
    /* Space for control panel */
}

/* Sidebar */
.sidebar {
    width: 200px;
    background-color: #2c2c2c;
    border-right: 1px solid #444;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 20px 10px;
    gap: 15px;
    /* Absolute Positioning for true centering of viewer */
    position: absolute;
    left: 0;
    top: 0;
    bottom: 60px;
    z-index: 1000;

    scrollbar-width: thin;
    scrollbar-color: #555 #2c2c2c;
    transition: width 0.3s ease, padding 0.3s ease, border-width 0.3s ease, transform 0.3s ease;
}

.sidebar.collapsed {
    width: 0;
    padding: 0;
    border-width: 0;
    overflow: hidden;
}

.sidebar::-webkit-scrollbar {
    width: 8px;
}

.sidebar::-webkit-scrollbar-track {
    background: #2c2c2c;
}

.sidebar::-webkit-scrollbar-thumb {
    background: #555;
    border-radius: 4px;
}

/* Sidebar Thumbnails */
.thumbnail-wrapper {
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    cursor: pointer;
    transition: transform 0.2s;
}

.thumbnail-wrapper:hover {
    transform: scale(1.05);
}

.thumbnail-canvas {
    width: 100%;
    border: 2px solid transparent;
    border-radius: 4px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
}

.thumbnail-wrapper.active .thumbnail-canvas {
    border-color: var(--accent-color);
    box-shadow: 0 0 10px var(--accent-color);
}

.thumbnail-label {
    color: #aaa;
    font-size: 0.8rem;
    margin-top: 5px;
}

.thumbnail-wrapper.active .thumbnail-label {
    color: var(--accent-color);
    font-weight: bold;
}

/* HYBRID RESPONSIVE LOGIC */

/* Default (Desktop) States */
.mobile-only {
    display: none !important;
}

.desktop-only {
    display: flex !important;
    /* or inline-flex */
}

/* Popover Stuff (Hidden by default, used in mobile) */
.control-popover {
    position: fixed;
    bottom: 80px;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(44, 44, 44, 0.95);
    padding: 10px 20px;
    border-radius: 8px;
    display: flex;
    gap: 10px;
    align-items: center;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.5);
    z-index: 1001;
    backdrop-filter: blur(5px);
    border: 1px solid #444;
}

.control-popover button {
    background: none;
    border: none;
    color: white;
    font-size: 1.2rem;
    cursor: pointer;
    padding: 5px;
}

.control-popover button:hover {
    color: var(--accent-color);
}

/* Media Queries */

/* Mobile Sidebar Overlay */
@media (max-width: 768px) {
    .sidebar {
        position: absolute;
        /* Overlay */
        left: 0;
        top: 0;
        bottom: 60px;
        /* Above control panel */
        width: 250px;
        /* Fixed width */
        z-index: 1500;
        background-color: #2c2c2c;
        box-shadow: 2px 0 15px rgba(0, 0, 0, 0.5);
        transform: translateX(0);
        /* Open State */
        display: flex;
        /* Ensure it's not hidden */
    }

    /* Mobile Collapsed State (Slide out) */
    .sidebar.collapsed {
        transform: translateX(-100%);
        width: 250px;
        /* Maintain width for slide */
        border: none;
        padding: 20px 10px;
        /* Keep padding */
    }
}

@media (max-width: 600px) {

    /* Switch to Mobile Mode */
    .mobile-only {
        display: flex !important;
    }

    .desktop-only {
        display: none !important;
    }

    .control-panel {
        padding: 0 15px;
        /* Add padding to prevent edge sticking */
        height: 60px;
        justify-content: space-between;
        /* Equal spacing between items */
    }

    .control-panel>div[style*="width"] {
        display: none;
        /* Hide spacers */
    }

    /* Flex Ordering for Perfect Centering */
    /* 1. Sidebar */
    #btnSidebarToggle {
        order: 1;
    }

    /* 2. Zoom */
    #btnZoomToggle {
        order: 2;
    }

    /* 3. Book (Center) */
    #btnNavToggle {
        order: 3;
    }

    /* 4. Download */
    #btnDownload {
        order: 4;
    }

    /* 5. Fullscreen */
    #btnFullscreen {
        order: 5;
    }

    .control-popover {
        width: 90%;
        justify-content: space-between;
    }
}