/* =====================================================
   CSS Variables & Reset
   ===================================================== */
:root {
    /* Colors */
    --primary: #4F46E5;
    --primary-dark: #4338CA;
    --primary-light: #6366F1;
    --success: #10B981;
    --success-dark: #059669;
    --error: #EF4444;
    --error-dark: #DC2626;
    --warning: #F59E0B;
    
    /* Neutral Colors */
    --gray-50: #F9FAFB;
    --gray-100: #F3F4F6;
    --gray-200: #E5E7EB;
    --gray-300: #D1D5DB;
    --gray-400: #9CA3AF;
    --gray-500: #6B7280;
    --gray-600: #4B5563;
    --gray-700: #374151;
    --gray-800: #1F2937;
    --gray-900: #111827;
    
    /* Light Theme (Default) */
    --bg-primary: #FFFFFF;
    --bg-secondary: var(--gray-50);
    --bg-tertiary: var(--gray-100);
    --text-primary: var(--gray-900);
    --text-secondary: var(--gray-600);
    --border-color: var(--gray-200);
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Transitions */
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-fast: all 0.15s ease;
}

/* Dark Theme */
body.dark-theme {
    --bg-primary: var(--gray-900);
    --bg-secondary: var(--gray-800);
    --bg-tertiary: var(--gray-700);
    --text-primary: var(--gray-50);
    --text-secondary: var(--gray-400);
    --border-color: var(--gray-700);
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -1px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -2px rgba(0, 0, 0, 0.2);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.3), 0 10px 10px -5px rgba(0, 0, 0, 0.2);
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* =====================================================
   Accessibility
   ===================================================== */
.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--primary);
    color: white;
    padding: 8px 16px;
    text-decoration: none;
    border-radius: 0 0 4px 0;
    z-index: 100;
}

.skip-link:focus {
    top: 0;
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* Focus indicators for accessibility */
*:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 2px;
}

button:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 2px;
}

/* =====================================================
   Header
   ===================================================== */
.header {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: var(--spacing-xl) 0;
    box-shadow: var(--shadow-lg);
    position: relative;
}

.header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--spacing-md);
}

.header-content {
    flex: 1;
}

.logo {
    font-size: 2rem;
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.tagline {
    font-size: 1rem;
    opacity: 0.95;
    font-weight: 400;
}

.theme-toggle {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    font-size: 1.5rem;
}

.theme-toggle:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: scale(1.1);
}

/* =====================================================
   Privacy Banner
   ===================================================== */
.privacy-banner {
    background: linear-gradient(135deg, var(--success) 0%, var(--success-dark) 100%);
    color: white;
    padding: var(--spacing-md) 0;
}

.privacy-content {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-md);
    font-size: 0.95rem;
}

.privacy-icon {
    width: 24px;
    height: 24px;
    flex-shrink: 0;
}

/* =====================================================
   Container & Layout
   ===================================================== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

.main {
    padding: var(--spacing-2xl) 0;
    min-height: calc(100vh - 400px);
}

/* =====================================================
   Upload Section
   ===================================================== */
.upload-section {
    margin-bottom: var(--spacing-2xl);
}

.upload-zone {
    background: var(--bg-primary);
    border: 3px dashed var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    text-align: center;
    transition: var(--transition);
    cursor: pointer;
    position: relative;
}

.upload-zone:hover,
.upload-zone.drag-over {
    border-color: var(--primary);
    background: var(--bg-secondary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.upload-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--spacing-lg);
    color: var(--primary);
    opacity: 0.8;
}

.upload-title {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.upload-text {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
}

.file-input {
    position: absolute;
    width: 1px;
    height: 1px;
    opacity: 0;
    pointer-events: none;
}

.browse-btn {
    background: var(--primary);
    color: white;
    border: none;
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow);
}

.browse-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

/* =====================================================
   Settings Panel
   ===================================================== */
.settings-panel {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-2xl);
    box-shadow: var(--shadow);
    animation: slideIn 0.4s ease-out;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.settings-title {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-lg);
    color: var(--text-primary);
}

.settings-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.setting-item {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.setting-item.full-width {
    grid-column: 1 / -1;
    flex-direction: row;
    gap: var(--spacing-xl);
}

.setting-label {
    font-weight: 600;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.quality-value {
    color: var(--primary);
    font-weight: 700;
}

.quality-slider {
    width: 100%;
    height: 8px;
    border-radius: var(--radius-sm);
    background: var(--gray-200);
    outline: none;
    -webkit-appearance: none;
}

.quality-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary);
    cursor: pointer;
    box-shadow: var(--shadow);
    transition: var(--transition-fast);
}

.quality-slider::-webkit-slider-thumb:hover {
    transform: scale(1.2);
    box-shadow: var(--shadow-lg);
}

.quality-slider::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary);
    cursor: pointer;
    border: none;
    box-shadow: var(--shadow);
    transition: var(--transition-fast);
}

.quality-slider::-moz-range-thumb:hover {
    transform: scale(1.2);
    box-shadow: var(--shadow-lg);
}

.slider-labels {
    display: flex;
    justify-content: space-between;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.format-selector,
.dimension-input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 1rem;
    transition: var(--transition-fast);
}

.format-selector:focus,
.dimension-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    cursor: pointer;
    color: var(--text-primary);
}

.checkbox-input {
    width: 18px;
    height: 18px;
    cursor: pointer;
    accent-color: var(--primary);
}

.settings-actions {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

/* =====================================================
   Buttons
   ===================================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-xl);
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow);
    white-space: nowrap;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none !important;
}

.btn-primary {
    background: var(--primary);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: var(--gray-200);
    color: var(--text-primary);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--gray-300);
    transform: translateY(-2px);
}

.btn-success {
    background: var(--success);
    color: white;
}

.btn-success:hover:not(:disabled) {
    background: var(--success-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-danger {
    background: var(--error);
    color: white;
}

.btn-danger:hover:not(:disabled) {
    background: var(--error-dark);
    transform: translateY(-2px);
}

.btn-icon {
    width: 20px;
    height: 20px;
}

.btn-download-all {
    width: 100%;
    margin-top: var(--spacing-lg);
    font-size: 1.125rem;
    padding: var(--spacing-lg) var(--spacing-xl);
}

/* =====================================================
   Statistics Dashboard
   ===================================================== */
.stats-dashboard {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-2xl);
    box-shadow: var(--shadow);
    animation: slideIn 0.4s ease-out;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-lg);
}

.stat-card {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    transition: var(--transition);
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.stat-highlight {
    background: linear-gradient(135deg, var(--success) 0%, var(--success-dark) 100%);
    color: white;
}

.stat-icon {
    font-size: 2rem;
    opacity: 0.9;
}

.stat-info {
    flex: 1;
}

.stat-label {
    font-size: 0.875rem;
    opacity: 0.8;
    margin-bottom: var(--spacing-xs);
}

.stat-highlight .stat-label {
    opacity: 0.95;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
}

/* =====================================================
   Results Section
   ===================================================== */
.results-section {
    animation: slideIn 0.4s ease-out;
}

.section-title {
    font-size: 1.75rem;
    margin-bottom: var(--spacing-xl);
    color: var(--text-primary);
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--spacing-xl);
}

.result-card {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
    animation: fadeIn 0.4s ease-out;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.result-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
}

.result-image-container {
    position: relative;
    width: 100%;
    padding-top: 75%; /* 4:3 aspect ratio */
    background: var(--gray-100);
    overflow: hidden;
}

.result-image {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: contain;
}

.result-status {
    position: absolute;
    top: var(--spacing-md);
    right: var(--spacing-md);
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    background: white;
    box-shadow: var(--shadow);
}

.result-status.pending {
    background: var(--warning);
    color: white;
}

.result-status.processing {
    background: var(--primary);
    color: white;
}

.result-status.completed {
    background: var(--success);
    color: white;
}

.result-status.error {
    background: var(--error);
    color: white;
}

.result-info {
    padding: var(--spacing-lg);
}

.result-name {
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    color: var(--text-primary);
}

.result-sizes {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--spacing-sm);
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.result-savings {
    display: inline-block;
    padding: var(--spacing-xs) var(--spacing-sm);
    background: var(--success);
    color: white;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
}

.result-progress {
    width: 100%;
    height: 6px;
    background: var(--gray-200);
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin-bottom: var(--spacing-md);
}

.result-progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--primary) 0%, var(--primary-light) 100%);
    transition: width 0.3s ease;
    border-radius: var(--radius-sm);
}

.result-actions {
    display: flex;
    gap: var(--spacing-sm);
}

.result-actions .btn {
    flex: 1;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.875rem;
}

/* =====================================================
   FAQ Section
   ===================================================== */
.faq-section {
    margin-top: var(--spacing-2xl);
    padding-top: var(--spacing-2xl);
    border-top: 2px solid var(--border-color);
}

.faq-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.faq-item {
    background: var(--bg-primary);
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
}

.faq-question {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.faq-answer {
    color: var(--text-secondary);
    line-height: 1.7;
}

/* =====================================================
   Footer
   ===================================================== */
.footer {
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-xl) 0;
    text-align: center;
    color: var(--text-secondary);
    margin-top: var(--spacing-2xl);
}

/* =====================================================
   Toast Notification
   ===================================================== */
.toast {
    position: fixed;
    bottom: var(--spacing-xl);
    right: var(--spacing-xl);
    background: var(--gray-900);
    color: white;
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-xl);
    transform: translateY(150%);
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 1000;
    max-width: 400px;
}

.toast.show {
    transform: translateY(0);
}

.toast.success {
    background: var(--success);
}

.toast.error {
    background: var(--error);
}

.toast.warning {
    background: var(--warning);
}

/* =====================================================
   Responsive Design
   ===================================================== */
@media (max-width: 768px) {
    .logo {
        font-size: 1.5rem;
    }
    
    .tagline {
        font-size: 0.875rem;
    }
    
    .header {
        padding: var(--spacing-lg) 0;
    }
    
    .upload-icon {
        width: 60px;
        height: 60px;
    }
    
    .upload-title {
        font-size: 1.25rem;
    }
    
    .settings-grid {
        grid-template-columns: 1fr;
    }
    
    .setting-item.full-width {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .settings-actions {
        flex-direction: column;
    }
    
    .settings-actions .btn {
        width: 100%;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .results-grid {
        grid-template-columns: 1fr;
    }
    
    .faq-grid {
        grid-template-columns: 1fr;
    }
    
    .toast {
        left: var(--spacing-md);
        right: var(--spacing-md);
        bottom: var(--spacing-md);
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-md);
    }
    
    .privacy-content {
        flex-direction: column;
        text-align: center;
        gap: var(--spacing-sm);
    }
    
    .result-actions {
        flex-direction: column;
    }
}

/* =====================================================
   Loading Animation
   ===================================================== */
@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

.spinner {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: white;
    animation: spin 0.8s linear infinite;
}

/* =====================================================
   Utilities
   ===================================================== */
.hidden {
    display: none !important;
}

.text-center {
    text-align: center;
}

.mt-1 {
    margin-top: var(--spacing-md);
}

.mt-2 {
    margin-top: var(--spacing-lg);
}

.mb-1 {
    margin-bottom: var(--spacing-md);
}

.mb-2 {
    margin-bottom: var(--spacing-lg);
}

/* =====================================================
   PWA Install Prompt
   ===================================================== */
.pwa-install-prompt {
    position: fixed;
    bottom: var(--spacing-xl);
    right: var(--spacing-xl);
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    z-index: 1000;
    max-width: 350px;
    animation: slideUp 0.3s ease-out;
}

@keyframes slideUp {
    from {
        transform: translateY(100px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.pwa-prompt-content {
    padding: var(--spacing-xl);
}

.pwa-prompt-content h3 {
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.pwa-prompt-content p {
    margin-bottom: var(--spacing-lg);
    color: var(--text-secondary);
}

.pwa-prompt-actions {
    display: flex;
    gap: var(--spacing-sm);
}

.pwa-prompt-actions .btn {
    flex: 1;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.875rem;
}

/* =====================================================
   Keyboard Navigation Support
   ===================================================== */
.upload-zone[tabindex]:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 4px;
}

/* =====================================================
   Responsive Design Improvements
   ===================================================== */
@media (max-width: 768px) {
    .logo {
        font-size: 1.5rem;
    }
    
    .tagline {
        font-size: 0.875rem;
    }
    
    .header {
        padding: var(--spacing-lg) 0;
    }
    
    .upload-icon {
        width: 60px;
        height: 60px;
    }
    
    .upload-title {
        font-size: 1.25rem;
    }
    
    .settings-grid {
        grid-template-columns: 1fr;
    }
    
    .setting-item.full-width {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .settings-actions {
        flex-direction: column;
    }
    
    .settings-actions .btn {
        width: 100%;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .results-grid {
        grid-template-columns: 1fr;
    }
    
    .faq-grid {
        grid-template-columns: 1fr;
    }
    
    .toast {
        left: var(--spacing-md);
        right: var(--spacing-md);
        bottom: var(--spacing-md);
    }
    
    .pwa-install-prompt {
        left: var(--spacing-md);
        right: var(--spacing-md);
        bottom: var(--spacing-md);
        max-width: none;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-md);
    }
    
    .privacy-content {
        flex-direction: column;
        text-align: center;
        gap: var(--spacing-sm);
    }
    
    .result-actions {
        flex-direction: column;
    }
    
    .header .container {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .theme-toggle {
        position: absolute;
        top: var(--spacing-md);
        right: var(--spacing-md);
    }
}

/* =====================================================
   Print Styles
   ===================================================== */
@media print {
    .header,
    .upload-section,
    .settings-panel,
    .toast,
    .pwa-install-prompt,
    .theme-toggle {
        display: none;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .results-section,
    .stats-dashboard {
        page-break-inside: avoid;
    }
}