/* --- General Body and Layout --- */
body {
    margin: 0;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    background: #f4f4f4;
    display: flex;
    flex-direction: column;
    align-items: center;
    user-select: none;
}

/* --- Book container (shifts when sidebar opens) --- */
.book-container {
    width: 100%;
    max-width: 1200px;
    box-sizing: border-box;
    transition: margin-left 0.35s ease;
}

/* When sidebar open, shift right (responsive auto width) */
.book-container.shifted {
    margin-left: clamp(220px, 30vw, 400px);
}

/* --- Index Sidebar (slides from left) --- */
#indexSidebar {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    background: #fdfdfd;
    border-right: 1px solid #ddd;
    overflow-y: auto;
    width: auto;
    max-width: 400px;
    min-width: 200px;
    padding: 12px 10px;
    transform: translateX(-100%);
    transition: transform 0.35s ease;
    z-index: 1600;
    box-shadow: 2px 0 18px rgba(0,0,0,0.08);
}
#indexSidebar.open {
    transform: translateX(0);
}

/* Sidebar content (indexMenu will populate) */
#indexMenu {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

/* Index items */
/* Note: You might not need .index-item if your JS uses .chapter directly */
.chapter { /* Changed from .index-item based on JS */
    border-bottom: 1px solid #f0f0f0;
    padding-bottom: 6px;
    margin-bottom: 6px;
}
.chapter:last-child { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }


.chapter-header { /* Changed from .index-chapter-header based on JS */
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.chapter-header .chapter-title { /* Kept .chapter-title, assuming it's inside */
    flex-grow: 1;
    font-weight: 600;
    font-size: 0.95rem;
    color: #000;
    text-align: left;
    cursor: pointer; /* Added cursor for title click */
    order: 1; /* <<< ADD THIS */
}

/* subsection toggle button */
.chapter-header .toggle-btn { /* Changed from .subsection-toggle based on JS */
    flex: 0 0 24px;       /* Keep the width you set */
    text-align: center;
    color: #007acc;
    background: transparent;
    border: none;
    font-weight: bold;
    cursor: pointer;
    font-size: 0.95em;    /* Makes the arrow ▸/▾ smaller */
    padding: 0;          /* Removes extra space inside the button */
    line-height: 1;      /* Helps vertically center the smaller arrow */
    order: 2; /* <<< ADD THIS */
}

/* subsection list inside sidebar - CORRECTED SELECTOR */
.subsections-list {
    display: none;
    padding-left: 12px;
    border-left: 3px solid #007acc;
    margin-left: 6px;
    margin-top: 6px;
    margin-bottom: 8px;
}
/* CORRECTED SELECTOR */
.subsections-list.visible {
    display: block;
}
/* CORRECTED SELECTOR */
.subsections-list .subsection { /* Changed from .subsection-link based on JS */
    font-size: 0.9rem;
    color: #444;
    padding: 6px 8px;
    margin: 2px 0;
    display: block;
    cursor: pointer;
    text-align: left;
}
/* CORRECTED SELECTOR */
.subsections-list .subsection:hover { /* Changed from .subsection-link based on JS */
    background: rgba(0, 122, 204, 0.05);
    color: #000;
}

/* --- Flipbook Container --- */
#flipbook {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    background: #fff;
    padding: 0;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    overflow: hidden;
    margin-top: 10px;
    margin-bottom: 80px;
    position: relative;
    z-index: 500;
}

/* --- The rest of your original CSS preserved / merged --- */

/* Page wrapper and image */
.page-wrap { position: relative; width: 100%; display: flex; justify-content: center; line-height: 0; transform-origin: center center; }
.page-image { width: 100%; height: auto; max-width: 100%; object-fit: contain; display: block; margin: 0 auto; border-radius: 6px; }

/* Highlight canvas */
#highlight-canvas { position: absolute; top: 0; left: 0; width: 100%; height: 100%; touch-action: none; pointer-events: none; }
body.highlight-mode #highlight-canvas { pointer-events: auto; }
#highlight-canvas.highlight-cursor { cursor: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="20" height="32" viewBox="0 0 20 32"><rect x="1" y="1" width="18" height="30" fill="none" stroke="black" stroke-width="2" stroke-dasharray="4 2"/></svg>') 10 16, crosshair; }
#highlight-canvas.eraser-cursor { cursor: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" viewBox="0 0 32 32"><circle cx="16" cy="16" r="14" fill="white" stroke="black" stroke-width="2"/></svg>') 16 16, cell; }

/* Lock screen */
#lockScreen { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.7); display: none; justify-content: center; align-items: center; z-index: 3000; }
.lock-box { background: #fff; padding: 2rem; border-radius: 8px; text-align: center; max-width: 300px; box-shadow: 0 4px 12px rgba(0,0,0,0.25); }
.lock-box input { width: 90%; padding: 0.5rem; font-size: 1rem; margin: 0.5rem 0; border: 1px solid #ccc; border-radius: 4px;}
.lock-box button { padding: 0.6rem 1.2rem; background: #007acc; color: #fff; border: none; border-radius: 6px; cursor: pointer; transition: background 0.2s; }
.lock-box button:hover { background: #005fa3; }

/* Toolbar */
.toolbar-container { position: sticky; top: 0; left: 0; width: 100%; z-index: 1000; background-color: #f0f0f0; padding: 8px; box-sizing: border-box; border-bottom: 1px solid #ddd; box-shadow: 0 2px 5px rgba(0,0,0,0.1); display: flex; flex-direction: column; align-items: center; }
.toolbar { margin-bottom: 8px; display: flex; justify-content: center; align-items: center; gap: 8px; flex-wrap: wrap; width: 100%; max-width: 1100px; }

/* Buttons */
button { padding: 5px 12px; border: none; border-radius: 6px; background: #007acc; color: white; font-size: 0.9rem; cursor: pointer; transition: background 0.18s, box-shadow 0.18s, opacity 0.18s, border-color 0.18s; white-space: nowrap; border: 3px solid transparent; }
button:hover { background: #005fa3; }
button:disabled { background-color: #b0b0b0; cursor: not-allowed; opacity: 0.7; }
button:active { transform: translateY(1px); }
button.active { background-color: #005fa3; }

/* Page input */
#pageInput { width: 60px; padding: 4px; font-size: 0.9rem; text-align: center; border: 1px solid #ccc; border-radius: 4px; }

/* Specific buttons */
#phetBtn { background: #d9534f; } #phetBtn:hover { background: #c9302c; }
#videoBtn { background: #28a745; } #videoBtn:hover { background: #218838; }
#searchBtn { font-size: 1.2rem; padding: 4px 8px; }
#toggle-draw-mode-btn { font-size: 1.1rem; padding: 4px 8px; }

/* Highlight group */
.highlight-buttons-group { display: flex; }
.highlight-buttons-group button { border-radius: 0; margin: 0; border: 3px solid transparent; }
.highlight-buttons-group button:first-child { border-top-left-radius: 6px; border-bottom-left-radius: 6px; }
.highlight-buttons-group button:last-child { border-top-right-radius: 6px; border-bottom-right-radius: 6px; border-left: 1px solid #005fa3; }

/* Activation styles */
#toggle-draw-mode-btn.active { background-color: #005fa3; border-color: #ffc107; box-shadow: 0 0 8px -2px #ffc107; }
#highlight-settings-btn.active { background-color: #005fa3; box-shadow: 0 0 6px 2px #ffc107 inset; border-color: #007acc; }

/* Popup */
.highlight-popup { display: none; position: absolute; top: 100%; margin-top: 5px; background-color: #ffffff; border: 1px solid #ccc; border-radius: 8px; box-shadow: 0 4px 12px rgba(0,0,0,0.15); padding: 10px; z-index: 1100; flex-direction: column; gap: 10px; opacity: 0; transform: translateY(-10px); transition: opacity 0.2s ease-out, transform 0.2s ease-out, visibility 0s linear 0.2s; visibility: hidden; min-width: 200px; }
.highlight-popup.visible { display: flex; opacity: 1; transform: translateY(0); visibility: visible; transition-delay: 0s; }
.popup-section { display: flex; align-items: center; gap: 8px; padding-bottom: 8px; border-bottom: 1px solid #eee; flex-wrap: wrap; }
.popup-section:last-child { border-bottom: none; padding-bottom: 0; }
.popup-section label { font-size: 0.9rem; color: #555; min-width: 40px; }
.popup-section input[type="range"] { flex-grow: 1; }
.popup-section button { background-color: #f0f0f0; color: #333; padding: 4px 10px; font-size: 0.85rem; border: 3px solid transparent; }
.popup-section button:hover { background-color: #ddd; }
.popup-section button.tool-btn.active { background-color: #007acc; color: white; box-shadow: none; border-color: #007acc;}
.color-swatches { display: flex; gap: 8px; flex-wrap: wrap; }
.color-swatch { width: 24px; height: 24px; border-radius: 50%; border: 2px solid #ccc; cursor: pointer; transition: transform 0.1s ease-out, border-color 0.1s; }
.color-swatch:hover { transform: scale(1.1); }
.color-swatch.active { border-color: #000; box-shadow: 0 0 0 2px white, 0 0 0 4px #000; }
.color-swatch[data-pen-color="#000000"] { background-clip: content-box; padding: 2px; }

/* Search area */
#searchContainer { width: 100%; max-width: 1100px; padding: 8px; box-sizing: border-box; background-color: #e9e9e9; border-radius: 0 0 8px 8px; box-shadow: 0 2px 4px rgba(0,0,0,0.1) inset; display: none; align-items: center; gap: 10px; margin-top: -8px; margin-bottom: 8px; position: relative; }
#searchInput { flex-grow: 1; padding: 6px 10px; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; }
#searchCloseBtn { background: none; border: none; font-size: 1.5rem; color: #888; cursor: pointer; padding: 0 5px; line-height: 1; }
#searchCloseBtn:hover { color: #333; }
#searchResults { position: absolute; top: 100%; left: 0; right: 0; max-height: 200px; overflow-y: auto; background: #fff; border: 1px solid #ccc; border-top: none; border-radius: 0 0 6px 6px; box-shadow: 0 4px 8px rgba(0,0,0,0.1); z-index: 1050; }
#searchResults div { padding: 8px 12px; font-size: 0.9rem; cursor: pointer; border-bottom: 1px solid #eee; }
#searchResults div:last-child { border-bottom: none; }
#searchResults div:hover { background-color: #f0f0f0; }
#searchResults .no-results { color: #888; padding: 10px; text-align: center; cursor: default; }

/* Thumbs */
.thumbbar { display: flex; overflow-x: auto; padding: 8px; background: #eee; border-top: 1px solid #ccc; border-bottom: 1px solid #ccc; gap: 8px; width: 100%; max-width: 1200px; box-sizing: border-box; position: relative; z-index: 499; min-height: 80px; }
.thumbbar img { height: 70px; cursor: pointer; border: 3px solid transparent; transition: border 0.18s; border-radius: 4px; box-shadow: 0 1px 3px rgba(0,0,0,0.1); }
.thumbbar img.active { border: 3px solid #007acc; }

/* Footer */
#footer { width: 100%; max-width: 100%; display: flex; align-items: center; justify-content: space-between; padding: 8px 16px; box-sizing: border-box; position: sticky; bottom: 0; left: 0; border-top: 1px solid #ddd; background-color: #f8f8f8; z-index: 500; }
.footer-left, .footer-right { display: flex; align-items: center; gap: 10px; }
#pageCounter { font-size: 1rem; color: #333; }
#indexToggle, #fullBtn, #shareBtn { padding: 5px 10px; font-size: 0.9rem; border: 3px solid transparent; }
#fullBtn { font-size: 1.2rem; }
#shareBtn { font-size: 1.1rem; }

/* AI Helper */
#aiHelperToggle { position: fixed; right: 20px; bottom: 65px; width: 50px; height: 50px; border-radius: 50%; font-size: 1.5rem; z-index: 2000; box-shadow: 0 4px 10px rgba(0,0,0,0.2); background-color: #6a0dad; color: white; border: 2px solid white; }
#aiHelperToggle:hover { background-color: #5a0bad; }
#aiHelperModal { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.5); display: none; justify-content: center; align-items: center; z-index: 2500; padding: 10px; box-sizing: border-box;}
.ai-content { background: #fff; padding: 1.5rem; border-radius: 12px; width: 95%; max-width: 550px; max-height: 90vh; overflow-y: auto; position: relative; box-shadow: 0 5px 15px rgba(0,0,0,0.3); }
#aiCloseBtn { position: absolute; top: 10px; right: 10px; background: #eee; color: #333; border-radius: 50%; width: 30px; height: 30px; padding: 0; line-height: 30px; text-align: center; cursor: pointer; border: none;}
#aiCloseBtn:hover { background: #ddd; }
.ai-buttons { display: flex; gap: 10px; margin: 1rem 0; flex-wrap: wrap; justify-content: center; }
.ai-buttons button { background-color: #f0f0f0; color: #333; font-size: 0.85rem; border: 3px solid transparent; }
.ai-buttons button:hover { background-color: #ddd; }
.ai-response { margin-top: 1rem; padding-top: 1rem; border-top: 1px solid #eee; white-space: pre-wrap; line-height: 1.6; font-size: 0.95rem; direction: ltr; text-align: left; }
#aiResponse.rtl-text { direction: rtl; text-align: right; }

/* Modals (PhET, Video) */
#phetModal, #videoModal { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.7); display: none; justify-content: center; align-items: center; z-index: 2600; padding: 15px; box-sizing: border-box; }
.phet-content { background: #fff; border-radius: 12px; width: 95%; height: 90vh; max-width: 1100px; position: relative; box-shadow: 0 5px 15px rgba(0,0,0,0.3); display: flex; flex-direction: column; }
.video-content { background: #000; border-radius: 12px; width: 95%; max-width: 1000px; aspect-ratio: 16 / 9; position: relative; box-shadow: 0 5px 20px rgba(0,0,0,0.4); display: flex; flex-direction: column; }
#phetCloseBtn, #videoCloseBtn { position: absolute; top: -15px; right: -15px; background: #333; color: #fff; border-radius: 50%; width: 35px; height: 35px; padding: 0; line-height: 35px; text-align: center; cursor: pointer; font-size: 1.2rem; border: 2px solid #fff; z-index: 10; }
#phetCloseBtn:hover, #videoCloseBtn:hover { background: #555; }
#phetFrame, #videoFrame { width: 100%; height: 100%; border: none; border-radius: 12px; }

/* Mobile adjustments */
@media (max-width: 768px) {
    .thumbbar img { height: 60px; gap: 6px; padding: 6px;}
    .toolbar { gap: 6px; }
    button { padding: 6px 10px; font-size: 0.9rem; }
    #pageInput { width: 50px; font-size: 0.9rem; }
    .footer-left, .footer-right { gap: 8px; }
    #pageCounter { font-size: 0.9rem; }
    #aiHelperToggle { width: 45px; height: 45px; font-size: 1.3rem; right: 15px; bottom: 60px; }
    .ai-content { padding: 1rem; }
    .highlight-popup { padding: 8px; gap: 8px; min-width: 180px;}
    .popup-section { gap: 6px; padding-bottom: 6px;}
    .popup-section label { min-width: 35px; }
    .color-swatch { width: 22px; height: 22px; }
    #searchContainer { padding: 6px; gap: 6px;}
    #searchInput { padding: 5px 8px; font-size: 0.85rem;}
    #searchCloseBtn { font-size: 1.3rem; }
    #searchResults { max-height: 150px; }
    #searchResults div { padding: 6px 10px; font-size: 0.85rem;}
    /* On small screens, make sidebar overlay instead of push */
    .book-container.shifted { margin-left: 0; }
    #indexSidebar { width: min(90vw, 360px); }
    #indexSidebar.open { box-shadow: 2px 0 30px rgba(0,0,0,0.45); }
}

@media (max-width: 480px) {
    .thumbbar img { height: 50px; }
    .toolbar button, #pageInput { font-size: 0.8rem; padding: 4px 8px;}
    #pageInput { width: 45px; }
    .toolbar { gap: 4px; }
    .highlight-buttons-group button { padding: 4px 8px; }
    #footer { padding: 6px 10px; }
    #pageCounter { font-size: 0.8rem; }
    .ai-content { width: 98%; padding: 0.8rem;}
    .ai-buttons button { font-size: 0.8rem; padding: 5px 8px;}
    #aiHelperToggle { bottom: 55px; }
}