/* Design System & Variables */
:root {
    /* Light Theme Variables (Default) */
    --bg-color: #f8fafc;
    --card-bg: rgba(255, 255, 255, 0.7);
    --card-border: rgba(99, 102, 241, 0.08);
    --card-border-active: rgba(99, 102, 241, 0.4);
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #64748b;
    --primary: #4f46e5;
    --primary-grad: linear-gradient(135deg, #4f46e5 0%, #7c3aed 100%);
    --primary-glow: rgba(79, 70, 229, 0.15);
    --primary-glow-thin: rgba(79, 70, 229, 0.08);
    --success: #10b981;
    --success-grad: linear-gradient(135deg, #10b981 0%, #047857 100%);
    --success-glow: rgba(16, 185, 129, 0.15);
    --success-bg-light: rgba(16, 185, 129, 0.04);
    --success-bg-medium: rgba(16, 185, 129, 0.08);
    --success-border-light: rgba(16, 185, 129, 0.15);
    --success-border-medium: rgba(16, 185, 129, 0.35);
    --danger: #ef4444;
    --danger-bg-light: rgba(239, 68, 68, 0.08);
    --accent: #0891b2;
    --accent-glow: rgba(8, 145, 178, 0.12);
    --font-heading: 'Outfit', 'Inter', sans-serif;
    --font-body: 'Inter', sans-serif;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    
    /* Overlays & Shadows */
    --overlay-bg: rgba(15, 23, 42, 0.02);
    --overlay-hover: rgba(15, 23, 42, 0.04);
    --overlay-border: rgba(15, 23, 42, 0.06);
    --overlay-border-hover: rgba(15, 23, 42, 0.12);
    --overlay-bg-active: rgba(79, 70, 229, 0.08);
    --shadow-main: 0 20px 40px rgba(15, 23, 42, 0.06);
    --slider-track: rgba(15, 23, 42, 0.06);
    
    /* Glow circles */
    --glow-bg-1: #6366f1;
    --glow-bg-2: #a855f7;
    --glow-opacity: 0.12;
    
    /* Disabled States */
    --disabled-opacity: 0.65;
}

[data-theme="dark"] {
    /* Dark Theme Variables */
    --bg-color: #080b11;
    --card-bg: rgba(17, 22, 37, 0.65);
    --card-border: rgba(255, 255, 255, 0.07);
    --card-border-active: rgba(99, 102, 241, 0.4);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --primary: #6366f1;
    --primary-grad: linear-gradient(135deg, #6366f1 0%, #a855f7 100%);
    --primary-glow: rgba(99, 102, 241, 0.45);
    --primary-glow-thin: rgba(99, 102, 241, 0.12);
    --success: #10b981;
    --success-grad: linear-gradient(135deg, #10b981 0%, #059669 100%);
    --success-glow: rgba(16, 185, 129, 0.35);
    --success-bg-light: rgba(16, 185, 129, 0.03);
    --success-bg-medium: rgba(16, 185, 129, 0.15);
    --success-border-light: rgba(16, 185, 129, 0.15);
    --success-border-medium: rgba(16, 185, 129, 0.35);
    --danger: #ef4444;
    --danger-bg-light: rgba(239, 68, 68, 0.1);
    --accent: #06b6d4;
    --accent-glow: rgba(6, 182, 212, 0.3);
    
    --overlay-bg: rgba(255, 255, 255, 0.02);
    --overlay-hover: rgba(255, 255, 255, 0.04);
    --overlay-border: rgba(255, 255, 255, 0.07);
    --overlay-border-hover: rgba(255, 255, 255, 0.15);
    --overlay-bg-active: rgba(99, 102, 241, 0.08);
    --shadow-main: 0 20px 40px rgba(0, 0, 0, 0.3);
    --slider-track: rgba(255, 255, 255, 0.1);
    
    --glow-bg-1: #6366f1;
    --glow-bg-2: #a855f7;
    --glow-opacity: 0.15;
    
    /* Disabled States */
    --disabled-opacity: 0.45;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-body);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow-x: hidden;
    padding: 2rem 1rem;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* Glowing Background Circles */
.glass-bg {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: -1;
    overflow: hidden;
    pointer-events: none;
}

.glass-bg::before, .glass-bg::after {
    content: '';
    position: absolute;
    border-radius: 50%;
    filter: blur(120px);
    opacity: var(--glow-opacity);
    transition: background-color 0.3s ease, opacity 0.3s ease;
}

.glass-bg::before {
    width: 400px;
    height: 400px;
    background: var(--glow-bg-1);
    top: -100px;
    left: -100px;
}

.glass-bg::after {
    width: 500px;
    height: 500px;
    background: var(--glow-bg-2);
    bottom: -150px;
    right: -150px;
}

/* Container */
.container {
    width: 100%;
    max-width: 680px;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 0.5rem;
    position: relative;
}

.theme-toggle {
    position: absolute;
    top: 5px;
    right: 5px;
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    width: 42px;
    height: 42px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.25rem;
    transition: var(--transition);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}

.theme-toggle:hover {
    background: var(--overlay-hover);
    border-color: var(--card-border-active);
    transform: scale(1.05);
}

.theme-icon-light {
    display: none;
}
.theme-icon-dark {
    display: block;
}

[data-theme="dark"] .theme-icon-light {
    display: block;
}
[data-theme="dark"] .theme-icon-dark {
    display: none;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.logo-icon {
    font-size: 2.25rem;
}

.logo h1 {
    font-family: var(--font-heading);
    font-size: 2.25rem;
    font-weight: 800;
    letter-spacing: -0.025em;
    color: var(--text-primary);
}

.logo h1 span {
    background: var(--primary-grad);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 0.95rem;
    max-width: 520px;
    margin: 0 auto;
    line-height: 1.5;
}

/* App Card */
.app-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: 24px;
    padding: 2rem;
    box-shadow: var(--shadow-main);
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* Upload Zone */
.drop-zone {
    border: 2px dashed var(--card-border);
    border-radius: 18px;
    padding: 2.5rem 1.5rem;
    text-align: center;
    position: relative;
    cursor: pointer;
    background: var(--overlay-bg);
    transition: var(--transition);
}

.drop-zone:hover, .drop-zone.dragover {
    border-color: var(--primary);
    background: var(--primary-glow-thin);
    box-shadow: inset 0 0 20px var(--primary-glow-thin);
}

.file-input {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    opacity: 0;
    cursor: pointer;
}

.drop-zone-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
    pointer-events: none;
}

.upload-icon {
    font-size: 2.5rem;
    margin-bottom: 0.25rem;
    filter: drop-shadow(0 4px 6px rgba(0, 0, 0, 0.1));
    transition: transform 0.2s ease;
}

.drop-zone:hover .upload-icon {
    transform: translateY(-4px);
}

.drop-zone h3 {
    font-family: var(--font-heading);
    font-size: 1.15rem;
    font-weight: 600;
}

.browse-text {
    color: var(--primary);
    font-weight: 500;
    text-decoration: underline;
}

.limit-text {
    color: var(--text-muted);
    font-size: 0.8rem;
    margin-top: 0.25rem;
}

/* Selected File Bar */
.file-info-bar {
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    border-radius: 12px;
    padding: 0.85rem 1.25rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    animation: slideIn 0.3s ease;
}

.file-icon {
    font-size: 1.25rem;
}

.file-name {
    font-weight: 500;
    font-size: 0.9rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    flex-grow: 1;
}

.file-size {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.btn-remove {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.5rem;
    cursor: pointer;
    line-height: 1;
    transition: var(--transition);
    padding: 0 0.25rem;
}

.btn-remove:hover {
    color: var(--danger);
    transform: scale(1.1);
}

/* Settings Section */
.settings-section.disabled {
    opacity: var(--disabled-opacity);
    pointer-events: none;
}

.section-title {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 1rem;
    letter-spacing: -0.01em;
}

/* Modes Grid */
.modes-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin-bottom: 1.5rem;
}

@media (min-width: 580px) {
    .modes-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

.mode-card {
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    border-radius: 14px;
    padding: 1.25rem 0.75rem;
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.4rem;
}

.mode-card:hover {
    border-color: var(--overlay-border-hover);
    background: var(--overlay-hover);
    transform: translateY(-2px);
}

.mode-card.active {
    border-color: var(--primary);
    background: var(--overlay-bg-active);
    box-shadow: 0 4px 20px var(--primary-glow);
}

.mode-icon {
    font-size: 1.5rem;
    margin-bottom: 0.2rem;
}

.mode-card h4 {
    font-family: var(--font-heading);
    font-size: 0.95rem;
    font-weight: 600;
}

.mode-card p {
    color: var(--text-secondary);
    font-size: 0.75rem;
}

.mode-badge {
    color: var(--accent);
    font-size: 0.7rem;
    font-weight: 600;
    background: var(--accent-glow);
    padding: 0.15rem 0.4rem;
    border-radius: 6px;
    margin-top: 0.25rem;
}

.mode-card.active .mode-badge {
    color: var(--text-primary);
    background: var(--primary-glow-thin);
}

/* Custom Panel */
.custom-panel {
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    border-radius: 16px;
    padding: 1.25rem;
    margin-bottom: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
    animation: fadeIn 0.3s ease;
}

.custom-panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 0.75rem;
    border-bottom: 1px solid var(--overlay-border);
    padding-bottom: 0.75rem;
}

.custom-panel-header h3 {
    font-size: 0.95rem;
    font-weight: 600;
}

/* Toggle Switch */
.toggle-container {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.toggle-label {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.switch {
    position: relative;
    display: inline-block;
    width: 38px;
    height: 22px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider-input, .slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--text-muted);
    transition: .4s;
}

.slider:before {
    position: absolute;
    content: "";
    height: 16px;
    width: 16px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    transition: .4s;
}

input:checked + .slider {
    background: var(--primary-grad);
}

input:checked + .slider:before {
    transform: translateX(16px);
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}

/* Control Groups */
.control-group {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    animation: fadeIn 0.2s ease;
}

.control-group label {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.input-with-unit {
    position: relative;
    display: flex;
    align-items: center;
    max-width: 140px;
}

.input-with-unit input {
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    color: var(--text-primary);
    padding: 0.5rem 2rem 0.5rem 0.75rem;
    border-radius: 8px;
    font-family: var(--font-body);
    font-size: 0.95rem;
    width: 100%;
}

.input-with-unit input:focus {
    border-color: var(--primary);
    outline: none;
    box-shadow: 0 0 10px var(--primary-glow);
}

.input-with-unit .unit {
    position: absolute;
    right: 0.75rem;
    font-size: 0.8rem;
    color: var(--text-muted);
    font-weight: 600;
}

.helper-text {
    font-size: 0.75rem;
    color: var(--text-muted);
    line-height: 1.4;
}

/* Sliders */
.slider-wrapper {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.slider-header {
    display: flex;
    justify-content: space-between;
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.slider-input {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 6px;
    border-radius: 3px;
    background: var(--slider-track);
    outline: none;
    position: relative;
}

.slider-input::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: var(--primary);
    cursor: pointer;
    box-shadow: 0 0 8px var(--primary-glow);
    transition: transform 0.1s ease;
}

.slider-input::-webkit-slider-thumb:hover {
    transform: scale(1.2);
}

/* Actions */
.action-container {
    margin-top: 0.5rem;
}

.btn {
    width: 100%;
    padding: 0.9rem 1.5rem;
    border: none;
    border-radius: 12px;
    color: var(--text-primary);
    font-family: var(--font-heading);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
    transition: var(--transition);
}

.btn-primary {
    background: var(--primary-grad);
    box-shadow: 0 4px 15px var(--primary-glow);
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px var(--primary-glow);
}

.btn-primary:active:not(:disabled) {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--overlay-bg-active);
    border: 1px solid var(--card-border-active);
    color: var(--primary);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--primary-glow-thin);
    border-color: var(--primary);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px var(--primary-glow-thin);
}

.btn-secondary:active:not(:disabled) {
    transform: translateY(0);
}

.form-row .btn {
    width: auto;
    white-space: nowrap;
    padding: 0.75rem 1.5rem;
}

.btn:disabled {
    opacity: var(--disabled-opacity);
    cursor: not-allowed;
    transform: none !important;
    box-shadow: none !important;
}

.arrow {
    transition: transform 0.2s ease;
}

.btn:hover .arrow {
    transform: translateX(4px);
}

/* Progress bar */
.progress-section {
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    border-radius: 16px;
    padding: 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.progress-info {
    display: flex;
    justify-content: space-between;
    font-size: 0.85rem;
    font-weight: 500;
}

#progress-status {
    color: var(--text-primary);
}

#progress-percent {
    color: var(--accent);
}

.progress-bar-bg {
    width: 100%;
    height: 8px;
    background: var(--slider-track);
    border-radius: 4px;
    overflow: hidden;
}

.progress-bar-fill {
    width: 0%;
    height: 100%;
    background: var(--primary-grad);
    border-radius: 4px;
    transition: width 0.1s ease;
}

.progress-bar-fill.pulsing {
    background-image: 
        repeating-linear-gradient(
            -45deg,
            transparent,
            transparent 10px,
            rgba(255, 255, 255, 0.15) 10px,
            rgba(255, 255, 255, 0.15) 20px
        ),
        var(--primary-grad);
    background-size: 28px 28px, 100% 100%;
    animation: 
        ripple-flow 0.8s linear infinite, 
        barPulse 1.2s ease-in-out infinite alternate;
}

@keyframes ripple-flow {
    0% { background-position: 0 0, 0 0; }
    100% { background-position: 28px 0, 0 0; }
}

@keyframes barPulse {
    0% {
        opacity: 0.6;
        box-shadow: 0 0 4px var(--primary-glow);
    }
    100% {
        opacity: 1.0;
        box-shadow: 0 0 15px var(--primary);
    }
}
.results-section {
    animation: slideIn 0.4s ease;
}

.results-card {
    background: var(--success-bg-light);
    border: 1px solid var(--success-border-light);
    border-radius: 18px;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.stats-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    border-radius: 12px;
    padding: 1rem 1.25rem;
}

.stat-box {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.stat-val {
    font-family: var(--font-heading);
    font-size: 1.25rem;
    font-weight: 700;
}

.stat-val.accent {
    color: var(--accent);
}

.stat-divider {
    color: var(--text-muted);
    font-size: 1.25rem;
    font-weight: 600;
}

.reduction-box {
    background: var(--success-bg-medium);
    padding: 0.35rem 0.75rem;
    border-radius: 8px;
    border: 1px solid var(--success-border-medium);
}

.stat-val.reduction {
    color: var(--success);
}

.btn-success {
    background: var(--success-grad);
    box-shadow: 0 4px 15px var(--success-glow);
}

.btn-success:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px var(--success-glow);
}

.btn-success:active {
    transform: translateY(0);
}

/* Footer styling */
footer {
    text-align: center;
    color: var(--text-muted);
    font-size: 0.75rem;
    line-height: 1.5;
    padding: 0 1rem;
}

/* Animations */
@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(12px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* Tabs Navigation */
.tabs-nav {
    display: flex;
    gap: 0.75rem;
    border-bottom: 1px solid var(--card-border);
    padding-bottom: 1rem;
    margin-bottom: 0.5rem;
}

.tab-btn {
    flex: 1;
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    padding: 0.75rem 1rem;
    border-radius: 12px;
    color: var(--text-secondary);
    font-family: var(--font-heading);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
    transition: var(--transition);
}

.tab-btn:hover {
    background: var(--overlay-hover);
    border-color: var(--overlay-border-hover);
    color: var(--text-primary);
}

.tab-btn.active {
    background: var(--overlay-bg-active);
    border-color: var(--primary);
    color: var(--text-primary);
    box-shadow: 0 4px 15px var(--primary-glow-thin);
}

.tab-icon {
    font-size: 1.1rem;
}

/* Merge Slots */
.merge-slots-container {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    margin-top: 1.25rem;
    margin-bottom: 1.5rem;
}

.merge-slot {
    position: relative;
    background: var(--overlay-bg);
    border: 1.5px dashed var(--card-border);
    border-radius: 14px;
    padding: 1rem 1.25rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    cursor: pointer;
    transition: var(--transition);
    overflow: hidden;
}

.merge-slot:hover {
    border-color: var(--card-border-active);
    background: var(--overlay-hover);
}

.merge-slot.filled {
    border-style: solid;
    border-color: var(--success-border-light);
    background: var(--success-bg-light);
}

.merge-slot.filled:hover {
    border-color: var(--success-border-medium);
    background: var(--success-bg-medium);
}

.merge-slot.dragover {
    border-color: var(--primary);
    background: var(--primary-glow-thin);
}

.merge-file-input {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    opacity: 0;
    cursor: pointer;
    z-index: 2;
}

.slot-badge {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    display: flex;
    justify-content: center;
    align-items: center;
    font-weight: 700;
    font-size: 0.85rem;
    color: var(--text-secondary);
    transition: var(--transition);
    flex-shrink: 0;
}

.merge-slot.filled .slot-badge {
    background: var(--success-bg-medium);
    border-color: var(--success);
    color: var(--success);
}

.slot-content {
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
    flex-grow: 1;
    pointer-events: none;
    min-width: 0;
}

.slot-text {
    font-size: 0.85rem;
    color: var(--text-secondary);
    transition: var(--transition);
}

.merge-slot.filled .slot-text {
    display: none;
}

.slot-file-name {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.slot-file-size {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.btn-clear-slot {
    position: relative;
    z-index: 3;
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.35rem;
    cursor: pointer;
    line-height: 1;
    transition: var(--transition);
    padding: 0.25rem;
    border-radius: 50%;
}

.btn-clear-slot:hover {
    color: var(--danger);
    background: var(--danger-bg-light);
    transform: scale(1.1);
}

/* Merge Summary Bar */
.merge-summary-bar {
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    border-radius: 12px;
    padding: 0.85rem 1.25rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
    animation: slideIn 0.3s ease;
}

.summary-icon {
    font-size: 1.25rem;
}

.summary-details {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-grow: 1;
    font-size: 0.9rem;
}

.total-size-indicator {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.merge-helper {
    margin-bottom: 0.5rem;
}

/* Advanced Optimizations Toggles */
.advanced-options-group {
    margin-top: 1.25rem;
    border-top: 1px solid var(--overlay-border);
    padding-top: 1rem;
}

.advanced-title {
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-secondary);
    letter-spacing: -0.01em;
}

.advanced-toggles {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

/* Visual Page Organizer */
.organizer-section {
    margin-top: 1.5rem;
    border-top: 1px solid var(--overlay-border);
    padding-top: 1.5rem;
    animation: slideIn 0.3s ease;
}

.pages-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
    gap: 1rem;
    margin-top: 1.25rem;
    margin-bottom: 1.5rem;
}

.page-card {
    position: relative;
    background: var(--overlay-bg);
    border: 1px solid var(--card-border);
    border-radius: 12px;
    padding: 0.6rem;
    text-align: center;
    cursor: grab;
    transition: var(--transition);
    user-select: none;
    -webkit-user-drag: element;
}

.page-card:hover {
    border-color: var(--card-border-active);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}

.page-card.dragging {
    opacity: 0.4;
    border-style: dashed;
    border-color: var(--primary);
    cursor: grabbing;
}

.page-thumbnail-container {
    position: relative;
    width: 100%;
    aspect-ratio: 1 / 1.414;
    background: #ffffff;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.08);
    display: flex;
    align-items: center;
    justify-content: center;
}

.page-thumbnail {
    width: 100%;
    height: 100%;
    object-fit: contain;
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.page-label-container {
    margin-top: 0.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.1rem;
    text-align: left;
}

.page-index-label {
    font-size: 0.75rem;
    font-weight: 700;
    color: var(--text-primary);
}

.page-source-label {
    font-size: 0.65rem;
    color: var(--text-muted);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* Overlays & Hover Actions */
.page-actions-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(15, 23, 42, 0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    opacity: 0;
    transition: opacity 0.2s ease;
    border-radius: 8px;
    z-index: 10;
}

.page-card:hover .page-actions-overlay {
    opacity: 1;
}

.action-overlay-btn {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    border: none;
    background: #ffffff;
    color: #0f172a;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 0.95rem;
    cursor: pointer;
    transition: transform 0.15s ease, background-color 0.15s ease;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
}

.action-overlay-btn:hover {
    transform: scale(1.1);
}

.action-overlay-btn.btn-rotate-page:hover {
    background: var(--primary);
    color: #ffffff;
}

.action-overlay-btn.btn-delete-page:hover {
    background: var(--danger);
    color: #ffffff;
}

/* Split Checkbox Selection Overlay */
.page-select-checkbox-container {
    position: absolute;
    top: 6px;
    right: 6px;
    z-index: 12;
    pointer-events: none;
}

.page-select-checkbox-container input[type="checkbox"] {
    pointer-events: auto;
    width: 18px;
    height: 18px;
    accent-color: var(--primary);
    cursor: pointer;
}

.page-card.selected {
    border-color: var(--primary);
    background: var(--overlay-bg-active);
    box-shadow: 0 4px 12px var(--primary-glow-thin);
}

/* Document Conversions Selector Cards */
/* Document Conversions Selector Cards */
.convert-mode-selector, .security-mode-selector {
    display: flex;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 1.75rem;
    flex-wrap: wrap;
}

.convert-mode-tab, .security-mode-tab {
    display: flex;
    flex: 1;
    min-width: 140px;
}

.convert-mode-card:hover {
    border-color: var(--card-border-active);
    color: var(--text-primary) !important;
}

.convert-mode-card.active {
    border-color: var(--primary) !important;
    background: var(--overlay-bg-active) !important;
    color: var(--text-primary) !important;
    box-shadow: 0 4px 12px var(--primary-glow-thin);
}

/* Document Security Selector Cards */
.security-mode-card:hover {
    border-color: var(--card-border-active);
    color: var(--text-primary) !important;
}

.security-mode-card.active {
    border-color: var(--primary) !important;
    background: var(--overlay-bg-active) !important;
    color: var(--text-primary) !important;
    box-shadow: 0 4px 12px var(--primary-glow-thin);
}

.page-card.touch-active .page-actions-overlay {
    opacity: 1;
}

/* SEO Info & Features Section */
.seo-info-section {
    margin-top: 1.5rem;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: 20px;
    padding: 1.5rem;
    box-shadow: var(--shadow-main);
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.seo-info-title {
    font-family: var(--font-heading);
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-primary);
}

.seo-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.seo-feature-card {
    background: var(--overlay-bg);
    border: 1px solid var(--overlay-border);
    border-radius: 12px;
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.seo-feature-card h3 {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--primary);
}

.seo-feature-card p {
    font-size: 0.78rem;
    color: var(--text-secondary);
    line-height: 1.4;
}

/* Mobile & Touch Responsive Design */
@media (max-width: 640px) {
    body {
        padding: 1rem 0.5rem;
    }

    .app-card {
        padding: 1.25rem 1rem;
        border-radius: 18px;
        gap: 1.25rem;
    }

    .tabs-nav {
        overflow-x: auto;
        white-space: nowrap;
        flex-wrap: nowrap;
        justify-content: flex-start;
        padding-bottom: 0.75rem;
        -webkit-overflow-scrolling: touch;
        scrollbar-width: none;
        -ms-overflow-style: none;
    }

    .tabs-nav::-webkit-scrollbar {
        display: none;
    }

    .tab-btn {
        flex: 0 0 auto;
        padding: 0.65rem 0.85rem;
        font-size: 0.85rem;
        min-height: 42px;
    }

    .drop-zone {
        padding: 1.75rem 1rem;
    }

    .modes-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 0.75rem;
    }

    .mode-card {
        padding: 1rem 0.5rem;
    }

    .split-actions-container {
        flex-direction: column;
        gap: 0.75rem;
    }

    .split-actions-container .btn {
        width: 100%;
    }

    .convert-mode-selector, .security-mode-selector {
        flex-direction: column;
        align-items: stretch;
        gap: 0.5rem;
    }

    .convert-mode-tab, .security-mode-tab {
        width: 100%;
    }

    .convert-mode-card, .security-mode-card {
        width: 100%;
        justify-content: center;
    }

    .settings-grid {
        grid-template-columns: 1fr !important;
        gap: 1rem !important;
    }

    .action-overlay-btn {
        width: 38px;
        height: 38px;
        font-size: 1.1rem;
    }
}

.hidden {
    display: none !important;
}

/* Service Status Banner */
.service-status-banner {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    padding: 0.75rem 1rem;
    background: var(--primary-glow-thin);
    border: 1px solid var(--primary-glow);
    border-radius: 12px;
    margin-bottom: 1.25rem;
    color: var(--text-primary);
    font-size: 0.85rem;
    font-weight: 500;
    transition: all 0.4s ease;
    opacity: 1;
    max-height: 50px;
    overflow: hidden;
}

.service-status-banner.hidden {
    opacity: 0 !important;
    max-height: 0 !important;
    padding-top: 0 !important;
    padding-bottom: 0 !important;
    margin-bottom: 0 !important;
    border-color: transparent !important;
    pointer-events: none !important;
}

.service-status-banner.error {
    background: rgba(239, 68, 68, 0.08);
    border-color: rgba(239, 68, 68, 0.2);
}

.spinner-mini {
    width: 14px;
    height: 14px;
    border: 2px solid rgba(255, 255, 255, 0.15);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin-mini 0.8s linear infinite;
    flex-shrink: 0;
}

.service-status-banner.error .spinner-mini {
    display: none;
}

@keyframes spin-mini {
    to { transform: rotate(360deg); }
}

/* Credit Key Settings Panel */
.credit-settings-panel {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: 20px;
    padding: 1.25rem;
    box-shadow: var(--shadow-main);
    transition: var(--transition);
}

.credit-settings-panel:hover {
    border-color: rgba(99, 102, 241, 0.15);
}

.credit-settings-panel.hidden {
    display: none !important;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
}

.panel-title-area {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.panel-title-area h3 {
    font-family: var(--font-heading);
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
}

.panel-icon {
    font-size: 1.25rem;
}

.panel-info-area {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.credit-balance-badge {
    background: var(--primary-glow-thin);
    color: var(--primary);
    border: 1px solid var(--primary-glow);
    padding: 0.35rem 0.75rem;
    border-radius: 99px;
    font-size: 0.85rem;
    font-weight: 600;
    letter-spacing: 0.02em;
}

.btn-toggle-panel {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 0.85rem;
    cursor: pointer;
    padding: 0.25rem;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.btn-toggle-panel .toggle-icon {
    display: inline-block;
    transition: transform 0.3s ease;
}

.btn-toggle-panel.open .toggle-icon {
    transform: rotate(180deg);
}

.panel-body {
    margin-top: 1.25rem;
    border-top: 1px solid var(--overlay-border);
    padding-top: 1.25rem;
    transition: var(--transition);
}

.credit-tabs {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1.25rem;
    background: none;
    padding: 0;
    border: none;
}

.credit-tab-btn {
    flex: 1;
    background: var(--overlay-bg);
    border: 1px solid var(--overlay-border);
    padding: 0.65rem 1rem;
    border-radius: 10px;
    font-family: var(--font-heading);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
}

.credit-tab-btn:hover {
    background: var(--overlay-hover);
    border-color: var(--overlay-border-hover);
    color: var(--text-primary);
}

.credit-tab-btn.active {
    background: var(--overlay-bg-active);
    border-color: var(--primary);
    color: var(--primary);
    box-shadow: 0 4px 12px var(--primary-glow-thin);
}

.credit-tab-content.hidden {
    display: none !important;
}

.credit-instructions {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.5;
}

.form-row {
    display: flex;
    gap: 0.75rem;
}

.form-row .text-input {
    flex: 1;
    padding: 0.75rem 1rem;
    border-radius: 10px;
    border: 1px solid var(--card-border);
    background: var(--overlay-bg);
    color: var(--text-primary);
    font-family: var(--font-body);
    font-size: 0.9rem;
    outline: none;
    transition: var(--transition);
}

.form-row .text-input:focus {
    border-color: var(--primary);
    background: var(--card-bg);
    box-shadow: 0 0 0 3px var(--primary-glow-thin);
}

.key-status-msg, .generate-status-msg {
    margin-top: 0.75rem;
    font-size: 0.85rem;
    font-weight: 500;
}

.key-status-msg.success, .generate-status-msg.success {
    color: var(--success);
}

.key-status-msg.error, .generate-status-msg.error {
    color: var(--danger);
}

.key-status-msg.info, .generate-status-msg.info {
    color: var(--accent);
}

/* Cost Badge in Buttons */
.btn-cost-badge {
    background: rgba(255, 255, 255, 0.15);
    color: currentColor;
    padding: 0.15rem 0.5rem;
    border-radius: 6px;
    font-size: 0.75rem;
    font-weight: 600;
    margin-left: 0.5rem;
    margin-right: 0.5rem;
    display: inline-block;
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
}

.btn-cost-badge.hidden {
    display: none !important;
}