:root {
    /* Light Mode Variables (Default) */
    --bg-color: #f1f3f5;
    --card-bg: rgba(255, 255, 255, 0.85);
    --card-border: rgba(0, 0, 0, 0.08);
    --text-primary: #1a1a1a;
    --text-secondary: #6c757d;
    --accent: #495057; 
    --accent-glow: rgba(73, 80, 87, 0.2);
    --secondary-accent: #ced4da; 
    
    /* Viewer Variables */
    --sidebar-w: 260px;
    --toolbar-h: 70px;
    --zoom: 1;
    --container-pad: 40px;
    --spread-gap: 10px;
    --scroll-behavior: smooth;
    --canvas-bg: #ffffff;
    --canvas-shadow: 0 10px 30px rgba(0,0,0,0.1);
}

body.dark {
    /* Dark Mode Variables */
    --bg-color: #0d0f14;
    --card-bg: rgba(26, 29, 39, 0.65);
    --card-border: rgba(255, 255, 255, 0.08);
    --text-primary: #f8f9fa;
    --text-secondary: #9ba1a6;
    --accent: #888;
    --accent-glow: rgba(136, 136, 136, 0.4);
    --secondary-accent: #333;
    --canvas-bg: #ffffff; /* Keep PDF pages white inside */
    --canvas-shadow: 0 10px 30px rgba(0,0,0,0.5);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    overflow: hidden;
    height: 100vh;
    height: 100dvh;
    display: flex;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* Background aesthetic orbs - Neutral Gray */
.background-elements {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    overflow: hidden;
    pointer-events: none;
    transition: opacity 0.3s;
}

.glow-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(80px);
    opacity: 0.3;
}

.orb-1 { top: -10%; left: -10%; width: 50vmin; height: 50vmin; background: #adb5bd; }
.orb-2 { bottom: -15%; right: -5%; width: 60vmin; height: 60vmin; background: #868e96; }
.orb-3 { top: 30%; left: 60%; width: 30vmin; height: 30vmin; background: #ced4da; opacity: 0.15; }

body.dark .orb-1 { background: #343a40; opacity: 0.5; }
body.dark .orb-2 { background: #212529; opacity: 0.5; }
body.dark .orb-3 { background: #495057; opacity: 0.2; }

/* Selector / Drop Zone */
#selector {
    position: fixed;
    inset: 0;
    z-index: 1000;
    background: var(--bg-color);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color 0.3s;
}

#selector.hidden { display: none; }

.action-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 20px;
    padding: 40px;
    backdrop-filter: blur(16px);
    box-shadow: 0 16px 32px rgba(0,0,0,0.1);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
body.dark .action-card { box-shadow: 0 16px 32px rgba(0,0,0,0.3); }

.drop-zone {
    width: 500px;
    height: 300px;
    border: 2px dashed var(--accent);
}

/* Base Buttons */
.btn-ui {
    background: rgba(0, 0, 0, 0.05);
    border: 1px solid var(--card-border);
    color: var(--text-primary);
    padding: 8px 16px;
    border-radius: 10px;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 500;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}
body.dark .btn-ui { background: rgba(255, 255, 255, 0.05); }

.btn-ui:hover {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
}

.icon-btn { padding: 8px; border-radius: 10px; height: 34px; width: 34px; }
.small-btn { padding: 4px 8px; min-width: 28px; }

/* Main App Layout */
#sidebar {
    width: var(--sidebar-w);
    height: 100%;
    background: var(--card-bg);
    border-right: 1px solid var(--card-border);
    backdrop-filter: blur(16px);
    overflow-y: auto;
    display: none;
    flex-direction: column;
    padding: 20px;
    z-index: 50;
    flex-shrink: 0;
}
#sidebar.visible { display: flex; }

.thumb {
    width: 100%;
    aspect-ratio: 1.4;
    background: #333;
    border-radius: 8px;
    cursor: pointer;
    margin-bottom: 15px;
    border: 2px solid transparent;
    font-size: 10px;
    font-weight: 600;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    transition: border-color 0.2s;
    overflow: hidden;
}
.thumb:hover { border-color: var(--accent); }

#main-view {
    flex-grow: 1;
    height: 100%;
    display: flex;
    flex-direction: column;
    position: relative;
    overflow: hidden;
}

/* Header / Toolbar */
.header-toolbar {
    height: var(--toolbar-h);
    background: var(--card-bg);
    border-bottom: 1px solid var(--card-border);
    backdrop-filter: blur(16px);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 24px;
    z-index: 100;
    flex-shrink: 0;
}

.logo { display: flex; align-items: center; gap: 0.5rem; color: var(--text-primary); }
.logo h1 { font-size: 1.2rem; font-weight: 700; letter-spacing: -0.5px; margin:0; }
.logo svg { stroke: var(--text-primary); }

.toolbar-controls {
    display: flex;
    align-items: center;
    gap: 20px;
}

.control-group {
    display: flex;
    align-items: center;
    gap: 12px;
    border-right: 1px solid var(--card-border);
    padding-right: 20px;
}
.control-group:last-child { border-right: none; padding-right: 0; }

.toggle-item {
    display: flex;
    align-items: center;
    gap: 6px;
}

.label { font-size: 0.75rem; font-weight: 600; color: var(--text-secondary); letter-spacing: 0.5px; }

.switch { position: relative; display: inline-block; width: 36px; height: 20px; }
.switch input { opacity: 0; width: 0; height: 0; }
.slider { position: absolute; cursor: pointer; inset: 0; background-color: rgba(0,0,0,0.2); border-radius: 20px; transition: .3s; }
body.dark .slider { background-color: rgba(255,255,255,0.2); }
.slider:before { position: absolute; content: ""; height: 16px; width: 16px; left: 2px; bottom: 2px; background-color: white; border-radius: 50%; transition: .3s; }
input:checked + .slider { background-color: var(--accent); }
input:checked + .slider:before { transform: translateX(16px); }

.value-display { font-size: 0.85rem; font-weight: 600; min-width: 45px; text-align: center; }

/* Select Base */
.select-wrapper { position: relative; }
.select-wrapper::after {
    content: '▼'; position: absolute; right: 10px; top: 50%;
    transform: translateY(-50%); font-size: 0.7rem; color: var(--text-secondary); pointer-events: none;
}
.slim-select select {
    appearance: none; background: rgba(0, 0, 0, 0.05); border: 1px solid var(--card-border);
    border-radius: 10px; padding: 6px 28px 6px 12px; color: var(--text-primary);
    font-size: 0.85rem; font-weight: 500; cursor: pointer; outline: none;
}
body.dark .slim-select select { background: rgba(255, 255, 255, 0.05); }

.global-actions { display: flex; gap: 8px; }

/* Scroll Area Details */
#scroll-area {
    flex-grow: 1;
    overflow: auto;
    scroll-behavior: var(--scroll-behavior);
    display: flex;
}

#zoom-wrapper {
    margin: auto;
    width: fit-content;
    height: fit-content;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: var(--container-pad);
    padding-bottom: calc(var(--container-pad) + 20px);
}

#container {
    width: fit-content;
    display: flex;
    flex-direction: column;
    gap: var(--container-gap, 60px);
}

.spread {
    display: flex;
    gap: calc(var(--spread-gap) * var(--fit-scale, 1) * var(--zoom));
    justify-content: center;
    align-items: center;
}

canvas {
    background: var(--canvas-bg);
    box-shadow: var(--canvas-shadow);
    display: block;
    border-radius: 4px;
    /* Dimensions are manipulated iteratively via inline styles linked to var(--fit-scale) */
}

.single-mode .spread { flex-direction: column; }

.no-padding { 
    --container-pad: 0px; 
    --spread-gap: 0px; 
    --container-gap: 0px;
}
.no-padding .spread { 
    margin: 0px; 
    padding: 0px;
}
.no-padding canvas { 
    box-shadow: none; 
    border-radius: 0; 
    display: block; 
    margin: 0;
}

/* Responsive adjustments */
@media (max-width: 1200px) {
    .toolbar-controls { flex-wrap: wrap; gap: 10px; }
    .control-group { padding-right: 10px; }
    .header-toolbar { padding: 10px 16px; height: auto; min-height: var(--toolbar-h); flex-wrap: wrap; gap: 15px; }
}