/* ============================================================================
   PowerPoint to PDF Converter - Main Stylesheet
   Professional, responsive design with support for all device sizes.
   ============================================================================ */

/* ============================================================================
   CSS CUSTOM PROPERTIES (DESIGN TOKENS)
   ============================================================================ */
:root {
    /* Colors */
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-primary-light: #3b82f6;
    --color-primary-bg: #eff6ff;
    --color-primary-border: #bfdbfe;
    
    --color-success: #22c55e;
    --color-success-bg: #dcfce7;
    --color-success-border: #bbf7d0;
    
    --color-warning: #f59e0b;
    --color-warning-bg: #fef3c7;
    --color-warning-border: #fde68a;
    
    --color-error: #ef4444;
    --color-error-bg: #fef2f2;
    --color-error-border: #fecaca;
    
    --color-orange: #d97706;
    --color-orange-bg: #fffbeb;
    
    /* Neutrals */
    --color-white: #ffffff;
    --color-gray-50: #f9fafb;
    --color-gray-100: #f3f4f6;
    --color-gray-200: #e5e7eb;
    --color-gray-300: #d1d5db;
    --color-gray-400: #9ca3af;
    --color-gray-500: #6b7280;
    --color-gray-600: #4b5563;
    --color-gray-700: #374151;
    --color-gray-800: #1f2937;
    --color-gray-900: #111827;
    
    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto Mono', monospace;
    
    /* Spacing */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
    --space-3xl: 64px;
    
    /* Border Radius */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;
    
    /* Layout */
    --max-width: 840px;
    --header-height: 64px;
}

/* ============================================================================
   RESET
   ============================================================================ */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-sans);
    background: var(--color-gray-50);
    color: var(--color-gray-800);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ============================================================================
   ACCESSIBILITY
   ============================================================================ */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* ============================================================================
   HEADER & NAVIGATION
   ============================================================================ */
.header {
    background: var(--color-white);
    border-bottom: 1px solid var(--color-gray-200);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    background: rgba(255, 255, 255, 0.95);
}

.header-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-lg);
    height: var(--header-height);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    text-decoration: none;
    color: var(--color-gray-900);
    font-weight: 700;
    font-size: 1.25rem;
}

.logo-icon {
    width: 32px;
    height: 32px;
}

.nav {
    position: relative;
}

.nav-list {
    display: flex;
    list-style: none;
    gap: var(--space-xs);
    align-items: center;
}

.nav-item {
    position: relative;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: var(--space-sm) var(--space-md);
    text-decoration: none;
    color: var(--color-gray-600);
    font-weight: 500;
    font-size: 0.9375rem;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    background: none;
    border: none;
    cursor: pointer;
    font-family: inherit;
}

.nav-link:hover {
    color: var(--color-primary);
    background: var(--color-primary-bg);
}

.nav-link.active {
    color: var(--color-primary);
    font-weight: 600;
}

.dropdown-arrow {
    transition: transform var(--transition-fast);
}

.nav-item.dropdown:hover .dropdown-arrow {
    transform: rotate(180deg);
}

/* Dropdown Menu */
.dropdown-menu {
    position: absolute;
    top: calc(100% + 8px);
    left: 50%;
    transform: translateX(-50%);
    background: var(--color-white);
    border: 1px solid var(--color-gray-200);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    padding: var(--space-lg);
    min-width: 620px;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-fast);
    z-index: 200;
}

.nav-item.dropdown:hover .dropdown-menu {
    opacity: 1;
    visibility: visible;
}

.dropdown-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-lg);
}

.dropdown-col {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs);
}

.dropdown-label {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-gray-400);
    margin-bottom: var(--space-xs);
    padding: 0 var(--space-sm);
}

.dropdown-link {
    padding: var(--space-sm) var(--space-md);
    text-decoration: none;
    color: var(--color-gray-600);
    font-size: 0.875rem;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.dropdown-link:hover {
    background: var(--color-gray-100);
    color: var(--color-gray-900);
}

.dropdown-link.active {
    background: var(--color-primary-bg);
    color: var(--color-primary);
    font-weight: 600;
}

/* Mobile Nav Toggle */
.nav-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
    border-radius: var(--radius-md);
}

.hamburger {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-gray-700);
    position: relative;
    transition: all var(--transition-base);
}

.hamburger::before,
.hamburger::after {
    content: '';
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-gray-700);
    position: absolute;
    transition: all var(--transition-base);
}

.hamburger::before { top: -7px; }
.hamburger::after { top: 7px; }

/* ============================================================================
   MAIN CONTENT
   ============================================================================ */
.main {
    flex: 1;
    padding-bottom: var(--space-3xl);
}

/* ============================================================================
   HERO SECTION
   ============================================================================ */
.hero {
    background: linear-gradient(135deg, var(--color-primary-bg) 0%, #f0f9ff 50%, #f5f3ff 100%);
    padding: var(--space-3xl) var(--space-lg) var(--space-2xl);
    text-align: center;
}

.hero-content {
    max-width: var(--max-width);
    margin: 0 auto;
}

.hero-title {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--color-gray-900);
    line-height: 1.2;
    margin-bottom: var(--space-md);
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 1.125rem;
    color: var(--color-gray-600);
    max-width: 640px;
    margin: 0 auto var(--space-lg);
    line-height: 1.7;
}

.hero-features {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--space-md);
}

.hero-feature {
    font-size: 0.875rem;
    color: var(--color-gray-500);
    background: rgba(255, 255, 255, 0.7);
    padding: var(--space-xs) var(--space-md);
    border-radius: var(--radius-full);
}

/* ============================================================================
   UPLOAD SECTION
   ============================================================================ */
.upload-section {
    max-width: var(--max-width);
    margin: calc(-1 * var(--space-xl)) auto 0;
    padding: 0 var(--space-lg);
    position: relative;
    z-index: 10;
}

.upload-container {
    background: var(--color-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    padding: var(--space-xl);
}

/* Upload Area */
.upload-area {
    border: 2px dashed var(--color-gray-300);
    border-radius: var(--radius-md);
    padding: var(--space-2xl) var(--space-lg);
    text-align: center;
    transition: all var(--transition-base);
    cursor: pointer;
    position: relative;
}

.upload-area:hover,
.upload-area.drag-over {
    border-color: var(--color-primary);
    background: var(--color-primary-bg);
}

.upload-area.drag-over {
    border-style: solid;
    background: #dbeafe;
    transform: scale(1.01);
}

.upload-icon {
    margin-bottom: var(--space-md);
}

.upload-heading {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-gray-800);
    margin-bottom: var(--space-xs);
}

.upload-hint {
    font-size: 0.9375rem;
    color: var(--color-gray-500);
    margin-bottom: var(--space-xs);
}

.upload-formats {
    font-size: 0.8125rem;
    color: var(--color-gray-400);
    margin-bottom: var(--space-md);
}

.file-input-hidden {
    position: absolute;
    inset: 0;
    opacity: 0;
    cursor: pointer;
}

.btn-upload {
    position: relative;
    z-index: 1;
}

/* File Preview */
.file-preview {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md);
    background: var(--color-orange-bg);
    border: 1px solid var(--color-warning-border);
    border-radius: var(--radius-md);
    margin-top: var(--space-md);
}

.file-preview-icon {
    flex-shrink: 0;
}

.file-preview-info {
    flex: 1;
    min-width: 0;
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.file-preview-name {
    font-weight: 600;
    color: var(--color-gray-800);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.file-preview-size {
    font-size: 0.8125rem;
    color: var(--color-gray-500);
}

.file-preview-hash {
    font-size: 0.75rem;
    color: var(--color-gray-400);
    font-family: var(--font-mono);
}

/* Quality Settings */
.quality-settings {
    margin-top: var(--space-lg);
    padding-top: var(--space-lg);
    border-top: 1px solid var(--color-gray-200);
}

.quality-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-md);
}

.quality-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-gray-800);
}

.quality-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-primary);
    min-width: 48px;
    text-align: right;
}

.quality-slider-container {
    margin-bottom: var(--space-md);
}

.quality-slider {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 8px;
    background: linear-gradient(to right, var(--color-success), var(--color-warning), var(--color-error));
    border-radius: 4px;
    outline: none;
    cursor: pointer;
}

.quality-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 24px;
    height: 24px;
    background: var(--color-white);
    border: 3px solid var(--color-primary);
    border-radius: 50%;
    cursor: pointer;
    box-shadow: var(--shadow-md);
    transition: transform var(--transition-fast);
}

.quality-slider::-webkit-slider-thumb:hover {
    transform: scale(1.15);
}

.quality-slider::-moz-range-thumb {
    width: 24px;
    height: 24px;
    background: var(--color-white);
    border: 3px solid var(--color-primary);
    border-radius: 50%;
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

.quality-labels {
    display: flex;
    justify-content: space-between;
    font-size: 0.75rem;
    color: var(--color-gray-400);
    margin-top: var(--space-xs);
}

.quality-presets {
    display: flex;
    gap: var(--space-sm);
    margin-bottom: var(--space-sm);
}

.quality-description {
    font-size: 0.875rem;
    color: var(--color-gray-500);
    margin-bottom: var(--space-xs);
}

.quality-estimate {
    font-size: 0.8125rem;
    color: var(--color-gray-400);
}

/* Action Area */
.action-area {
    margin-top: var(--space-lg);
    text-align: center;
}

/* ============================================================================
   BUTTONS
   ============================================================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-lg);
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.9375rem;
    font-family: inherit;
    cursor: pointer;
    transition: all var(--transition-fast);
    border: 2px solid transparent;
    text-decoration: none;
    line-height: 1.5;
    white-space: nowrap;
}

.btn:active {
    transform: scale(0.97);
}

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

.btn-primary:hover {
    background: var(--color-primary-dark);
    border-color: var(--color-primary-dark);
}

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

.btn-outline:hover {
    background: var(--color-primary-bg);
}

.btn-remove {
    background: none;
    border: none;
    color: var(--color-gray-400);
    padding: var(--space-xs);
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.btn-remove:hover {
    color: var(--color-error);
    background: var(--color-error-bg);
}

.btn-preset {
    background: var(--color-gray-100);
    color: var(--color-gray-600);
    border: 2px solid transparent;
    padding: var(--space-xs) var(--space-md);
    font-size: 0.8125rem;
}

.btn-preset:hover {
    background: var(--color-gray-200);
    color: var(--color-gray-800);
}

.btn-preset.active {
    background: var(--color-primary-bg);
    color: var(--color-primary);
    border-color: var(--color-primary);
}

.btn-convert {
    background: var(--color-success);
    color: var(--color-white);
    border-color: var(--color-success);
    padding: var(--space-md) var(--space-2xl);
    font-size: 1.125rem;
}

.btn-convert:hover {
    background: #16a34a;
    border-color: #16a34a;
    box-shadow: 0 4px 12px rgba(34, 197, 94, 0.4);
}

.btn-download {
    background: var(--color-primary);
    color: var(--color-white);
    border-color: var(--color-primary);
    padding: var(--space-md) var(--space-2xl);
    font-size: 1.125rem;
}

.btn-download:hover {
    background: var(--color-primary-dark);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.4);
}

/* ============================================================================
   PROGRESS SECTION
   ============================================================================ */
.progress-section {
    max-width: var(--max-width);
    margin: var(--space-xl) auto 0;
    padding: 0 var(--space-lg);
}

.progress-container {
    background: var(--color-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: var(--space-xl);
}

.progress-status {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    margin-bottom: var(--space-md);
}

.progress-icon {
    flex-shrink: 0;
}

.spinner {
    animation: spin 1s linear infinite;
}

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

.progress-message {
    font-size: 1rem;
    font-weight: 500;
    color: var(--color-gray-700);
}

.progress-bar-container {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.progress-bar {
    flex: 1;
    height: 12px;
    background: var(--color-gray-200);
    border-radius: var(--radius-full);
    overflow: hidden;
}

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

.progress-percent {
    font-weight: 700;
    font-size: 1rem;
    color: var(--color-primary);
    min-width: 48px;
    text-align: right;
}

.progress-details {
    display: flex;
    justify-content: space-between;
    margin-top: var(--space-sm);
    font-size: 0.8125rem;
    color: var(--color-gray-400);
}

/* ============================================================================
   RESULTS SECTION
   ============================================================================ */
.results-section {
    max-width: var(--max-width);
    margin: var(--space-xl) auto 0;
    padding: 0 var(--space-lg);
}

.results-container {
    background: var(--color-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: var(--space-2xl);
    text-align: center;
}

.results-icon {
    margin-bottom: var(--space-md);
}

.results-heading {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-success);
    margin-bottom: var(--space-sm);
}

.results-info {
    font-size: 1rem;
    color: var(--color-gray-500);
    margin-bottom: var(--space-lg);
}

.results-stats {
    display: flex;
    justify-content: center;
    gap: var(--space-xl);
    margin-bottom: var(--space-xl);
    flex-wrap: wrap;
}

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

.result-stat-value {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-gray-800);
}

.result-stat-label {
    font-size: 0.75rem;
    color: var(--color-gray-400);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.results-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ============================================================================
   ERROR SECTION
   ============================================================================ */
.error-section {
    max-width: var(--max-width);
    margin: var(--space-xl) auto 0;
    padding: 0 var(--space-lg);
}

.error-container {
    background: var(--color-white);
    border: 1px solid var(--color-error-border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: var(--space-2xl);
    text-align: center;
}

.error-container .error-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 64px;
    height: 64px;
    background: var(--color-error-bg);
    border-radius: 50%;
    margin: 0 auto var(--space-md);
    font-size: 32px;
    color: var(--color-error);
}

.error-heading {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-error);
    margin-bottom: var(--space-sm);
}

.error-message {
    font-size: 0.9375rem;
    color: var(--color-gray-500);
    margin-bottom: var(--space-lg);
}

/* ============================================================================
   FEATURES SECTION
   ============================================================================ */
.features-section {
    max-width: 1000px;
    margin: var(--space-3xl) auto 0;
    padding: 0 var(--space-lg);
}

.section-heading {
    text-align: center;
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--color-gray-900);
    margin-bottom: var(--space-2xl);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.feature-card {
    background: var(--color-white);
    border: 1px solid var(--color-gray-200);
    border-radius: var(--radius-md);
    padding: var(--space-xl) var(--space-lg);
    text-align: center;
    transition: all var(--transition-base);
}

.feature-card:hover {
    box-shadow: var(--shadow-lg);
    border-color: var(--color-primary-border);
    transform: translateY(-2px);
}

.feature-icon {
    margin-bottom: var(--space-md);
    display: inline-flex;
    padding: var(--space-md);
    background: var(--color-primary-bg);
    border-radius: var(--radius-md);
}

.feature-title {
    font-size: 1.0625rem;
    font-weight: 600;
    color: var(--color-gray-800);
    margin-bottom: var(--space-sm);
}

.feature-text {
    font-size: 0.875rem;
    color: var(--color-gray-500);
    line-height: 1.6;
}

/* ============================================================================
   FAQ SECTION
   ============================================================================ */
.faq-section {
    max-width: 760px;
    margin: var(--space-3xl) auto 0;
    padding: 0 var(--space-lg);
}

.faq-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.faq-item {
    background: var(--color-white);
    border: 1px solid var(--color-gray-200);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.faq-question {
    width: 100%;
    padding: var(--space-md) var(--space-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: none;
    border: none;
    cursor: pointer;
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--color-gray-800);
    font-family: inherit;
    text-align: left;
    transition: background var(--transition-fast);
}

.faq-question:hover {
    background: var(--color-gray-50);
}

.faq-arrow {
    flex-shrink: 0;
    transition: transform var(--transition-fast);
    color: var(--color-gray-400);
}

.faq-item.active .faq-arrow {
    transform: rotate(180deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-slow), padding var(--transition-slow);
}

.faq-item.active .faq-answer {
    max-height: 300px;
    padding: 0 var(--space-lg) var(--space-md);
}

.faq-answer p {
    font-size: 0.875rem;
    color: var(--color-gray-500);
    line-height: 1.7;
}

/* ============================================================================
   FOOTER
   ============================================================================ */
.footer {
    background: var(--color-white);
    border-top: 1px solid var(--color-gray-200);
    padding: var(--space-lg);
    margin-top: var(--space-3xl);
}

.footer-inner {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: var(--space-md);
    font-size: 0.875rem;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-weight: 600;
    color: var(--color-gray-700);
}

.footer-copy {
    color: var(--color-gray-400);
}

.footer-nav {
    display: flex;
    gap: var(--space-md);
}

.footer-nav a {
    color: var(--color-gray-500);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.footer-nav a:hover {
    color: var(--color-primary);
}

/* ============================================================================
   TOAST NOTIFICATIONS
   ============================================================================ */
.toast-container {
    position: fixed;
    bottom: var(--space-lg);
    right: var(--space-lg);
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
    pointer-events: none;
}

.toast {
    background: var(--color-white);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    padding: var(--space-md) var(--space-lg);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.875rem;
    font-weight: 500;
    pointer-events: auto;
    animation: toastIn 0.3s ease;
    max-width: 360px;
}

.toast.removing {
    animation: toastOut 0.3s ease forwards;
}

.toast-info {
    border-left: 4px solid var(--color-primary);
    color: var(--color-gray-700);
}

.toast-success {
    border-left: 4px solid var(--color-success);
    color: var(--color-gray-700);
}

.toast-error {
    border-left: 4px solid var(--color-error);
    color: var(--color-gray-700);
}

.toast-warning {
    border-left: 4px solid var(--color-warning);
    color: var(--color-gray-700);
}

@keyframes toastIn {
    from {
        opacity: 0;
        transform: translateX(100%);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes toastOut {
    from {
        opacity: 1;
        transform: translateX(0);
    }
    to {
        opacity: 0;
        transform: translateX(100%);
    }
}

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

/* ============================================================================
   RESPONSIVE - TABLET (max-width: 768px)
   ============================================================================ */
@media (max-width: 768px) {
    :root {
        --header-height: 56px;
    }
    
    /* Navigation */
    .nav-toggle {
        display: block;
    }
    
    .nav-list {
        position: fixed;
        top: var(--header-height);
        left: 0;
        right: 0;
        bottom: 0;
        background: var(--color-white);
        flex-direction: column;
        padding: var(--space-lg);
        gap: var(--space-xs);
        transform: translateX(100%);
        transition: transform var(--transition-base);
        overflow-y: auto;
        z-index: 99;
    }
    
    .nav-list.open {
        transform: translateX(0);
    }
    
    .dropdown-menu {
        position: static;
        transform: none;
        opacity: 1;
        visibility: visible;
        box-shadow: none;
        border: none;
        padding: var(--space-sm) 0;
        min-width: unset;
    }
    
    .dropdown-grid {
        grid-template-columns: 1fr;
        gap: var(--space-md);
    }
    
    /* Hero */
    .hero {
        padding: var(--space-2xl) var(--space-md) var(--space-xl);
    }
    
    .hero-title {
        font-size: 1.75rem;
    }
    
    .hero-subtitle {
        font-size: 1rem;
    }
    
    .hero-features {
        flex-direction: column;
        align-items: center;
        gap: var(--space-xs);
    }
    
    /* Upload */
    .upload-section {
        margin-top: calc(-1 * var(--space-lg));
        padding: 0 var(--space-md);
    }
    
    .upload-container {
        padding: var(--space-lg);
    }
    
    .upload-area {
        padding: var(--space-xl) var(--space-md);
    }
    
    /* Features */
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--space-md);
    }
    
    .section-heading {
        font-size: 1.5rem;
    }
    
    /* Results */
    .results-actions {
        flex-direction: column;
    }
    
    .results-stats {
        gap: var(--space-md);
    }
    
    /* FAQ */
    .faq-question {
        font-size: 0.875rem;
        padding: var(--space-sm) var(--space-md);
    }
    
    /* Footer */
    .footer-inner {
        flex-direction: column;
        text-align: center;
    }
}

/* ============================================================================
   RESPONSIVE - MOBILE (max-width: 480px)
   ============================================================================ */
@media (max-width: 480px) {
    .hero-title {
        font-size: 1.375rem;
    }
    
    .upload-heading {
        font-size: 1.0625rem;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .quality-presets {
        flex-wrap: wrap;
    }
    
    .btn-preset {
        flex: 1;
        min-width: calc(50% - var(--space-xs));
    }
    
    .btn-convert,
    .btn-download {
        width: 100%;
        padding: var(--space-md);
        font-size: 1rem;
    }
    
    .toast-container {
        left: var(--space-md);
        right: var(--space-md);
        bottom: var(--space-md);
    }
    
    .toast {
        max-width: 100%;
    }
    
    .progress-details {
        flex-direction: column;
        align-items: center;
    }
}