/* ==========================================
   GLOBAL STYLES & RESET
   ========================================== */

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

:root {
    /* Color Palette */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    
    /* Neutral Colors */
    --white: #ffffff;
    --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;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 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);
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 300ms ease-in-out;
    --transition-slow: 500ms ease-in-out;
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
}

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

/* ==========================================
   CONTAINER & LAYOUT
   ========================================== */

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.main-content {
    flex: 1;
    padding: var(--spacing-xl) 0;
}

/* ==========================================
   HEADER
   ========================================== */

.header {
    background: var(--primary-gradient);
    color: var(--white);
    padding: var(--spacing-2xl) 0;
    box-shadow: var(--shadow-lg);
    text-align: center;
}

.header-content {
    animation: fadeInDown 0.6s ease-out;
}

.logo {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-md);
}

.logo-icon {
    font-size: 3rem;
    animation: bounce 2s infinite;
}

.tagline {
    font-size: 1.125rem;
    opacity: 0.95;
    font-weight: 300;
}

/* ==========================================
   SECTIONS
   ========================================== */

.intro-section {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
    animation: fadeIn 0.8s ease-out;
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: var(--spacing-md);
}

.section-description {
    font-size: 1.125rem;
    color: var(--gray-600);
    max-width: 700px;
    margin: 0 auto;
}

/* ==========================================
   UPLOAD SECTION
   ========================================== */

.upload-section {
    margin-bottom: var(--spacing-2xl);
    animation: fadeInUp 0.8s ease-out 0.2s both;
}

.upload-area {
    background: var(--white);
    border: 3px dashed var(--gray-300);
    border-radius: var(--radius-2xl);
    padding: var(--spacing-3xl);
    text-align: center;
    transition: all var(--transition-base);
    cursor: pointer;
}

.upload-area:hover {
    border-color: #667eea;
    background: var(--gray-50);
    transform: translateY(-2px);
}

.upload-area.dragover {
    border-color: #667eea;
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.1) 0%, rgba(118, 75, 162, 0.1) 100%);
    transform: scale(1.02);
}

.upload-icon {
    font-size: 4rem;
    margin-bottom: var(--spacing-md);
    animation: float 3s ease-in-out infinite;
}

.upload-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: var(--spacing-sm);
}

.upload-text {
    color: var(--gray-600);
    margin-bottom: var(--spacing-xl);
}

.upload-note {
    margin-top: var(--spacing-lg);
    color: var(--gray-500);
    font-size: 0.875rem;
}

/* ==========================================
   BUTTONS
   ========================================== */

.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
    box-shadow: var(--shadow-md);
}

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

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

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

.btn-secondary {
    background: var(--white);
    color: var(--gray-700);
    border: 2px solid var(--gray-300);
}

.btn-secondary:hover {
    border-color: var(--gray-400);
    background: var(--gray-50);
}

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

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

.btn-small {
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.875rem;
}

.btn-large {
    padding: var(--spacing-lg) var(--spacing-2xl);
    font-size: 1.125rem;
}

.btn-icon {
    font-size: 1.2em;
}

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

/* ==========================================
   FILES SECTION
   ========================================== */

.files-section {
    animation: fadeInUp 0.6s ease-out;
}

.files-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-lg);
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.files-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--gray-900);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.files-icon {
    font-size: 1.5rem;
}

.files-instruction {
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.1) 0%, rgba(118, 75, 162, 0.1) 100%);
    padding: var(--spacing-md);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-lg);
    text-align: center;
    color: var(--gray-700);
}

.files-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-2xl);
}

.file-item {
    background: var(--white);
    border: 2px solid var(--gray-200);
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    transition: all var(--transition-base);
    cursor: move;
}

.file-item:hover {
    border-color: #667eea;
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.file-item.dragging {
    opacity: 0.5;
    transform: scale(0.95);
}

.file-drag-handle {
    font-size: 1.5rem;
    color: var(--gray-400);
    cursor: grab;
}

.file-drag-handle:active {
    cursor: grabbing;
}

.file-icon {
    font-size: 2.5rem;
    flex-shrink: 0;
}

.file-info {
    flex: 1;
    min-width: 0;
}

.file-name {
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: var(--spacing-xs);
    word-break: break-word;
}

.file-size {
    font-size: 0.875rem;
    color: var(--gray-500);
}

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

.btn-icon-only {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: var(--spacing-sm);
    transition: all var(--transition-fast);
    border-radius: var(--radius-md);
}

.btn-icon-only:hover {
    background: var(--gray-100);
    transform: scale(1.1);
}

.btn-remove:hover {
    background: rgba(239, 68, 68, 0.1);
}

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

/* ==========================================
   PROGRESS SECTION
   ========================================== */

.progress-section {
    animation: fadeIn 0.6s ease-out;
}

.progress-container {
    background: var(--white);
    border-radius: var(--radius-2xl);
    padding: var(--spacing-3xl);
    text-align: center;
    box-shadow: var(--shadow-lg);
}

.progress-icon {
    font-size: 4rem;
    margin-bottom: var(--spacing-lg);
    animation: spin 2s linear infinite;
}

.progress-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: var(--spacing-md);
}

.progress-bar {
    width: 100%;
    height: 12px;
    background: var(--gray-200);
    border-radius: 999px;
    overflow: hidden;
    margin-bottom: var(--spacing-md);
}

.progress-fill {
    height: 100%;
    background: var(--primary-gradient);
    border-radius: 999px;
    transition: width var(--transition-base);
    animation: progressPulse 1.5s ease-in-out infinite;
}

.progress-text {
    color: var(--gray-600);
}

/* ==========================================
   SUCCESS SECTION
   ========================================== */

.success-section {
    animation: fadeIn 0.6s ease-out;
}

.success-container {
    background: var(--white);
    border-radius: var(--radius-2xl);
    padding: var(--spacing-3xl);
    text-align: center;
    box-shadow: var(--shadow-lg);
}

.success-icon {
    font-size: 5rem;
    margin-bottom: var(--spacing-lg);
    animation: scaleIn 0.6s ease-out;
}

.success-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--success-color);
    margin-bottom: var(--spacing-md);
}

.success-text {
    color: var(--gray-600);
    margin-bottom: var(--spacing-2xl);
    font-size: 1.125rem;
}

/* ==========================================
   FEATURES SECTION
   ========================================== */

.features-section {
    margin: var(--spacing-3xl) 0;
    text-align: center;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-xl);
    margin-top: var(--spacing-2xl);
}

.feature-card {
    background: var(--white);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    transition: all var(--transition-base);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.feature-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: var(--spacing-sm);
}

.feature-description {
    color: var(--gray-600);
    line-height: 1.7;
}

/* ==========================================
   HOW TO SECTION
   ========================================== */

.howto-section {
    margin: var(--spacing-3xl) 0;
    text-align: center;
}

.steps-container {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-xl);
    margin-top: var(--spacing-2xl);
}

.step {
    background: var(--white);
    padding: var(--spacing-xl);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    max-width: 250px;
    transition: all var(--transition-base);
}

.step:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.step-number {
    width: 50px;
    height: 50px;
    background: var(--primary-gradient);
    color: var(--white);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
    margin: 0 auto var(--spacing-md);
}

.step-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: var(--spacing-sm);
}

.step-description {
    color: var(--gray-600);
    font-size: 0.875rem;
}

.step-arrow {
    font-size: 2rem;
    color: var(--gray-400);
}

/* ==========================================
   PRIVACY SECTION
   ========================================== */

.privacy-section {
    margin: var(--spacing-3xl) 0;
}

.privacy-card {
    background: linear-gradient(135deg, rgba(16, 185, 129, 0.1) 0%, rgba(5, 150, 105, 0.1) 100%);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-xl);
    border: 2px solid rgba(16, 185, 129, 0.3);
}

.privacy-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.privacy-text {
    color: var(--gray-700);
    line-height: 1.8;
}

/* ==========================================
   FOOTER
   ========================================== */

.footer {
    background: var(--gray-900);
    color: var(--gray-400);
    padding: var(--spacing-2xl) 0;
    text-align: center;
    margin-top: auto;
}

.footer-text {
    margin-bottom: var(--spacing-sm);
}

.footer-links a {
    color: #667eea;
    text-decoration: none;
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: #764ba2;
    text-decoration: underline;
}

/* ==========================================
   TOAST NOTIFICATION
   ========================================== */

.toast {
    position: fixed;
    bottom: var(--spacing-xl);
    right: var(--spacing-xl);
    background: var(--white);
    color: var(--gray-900);
    padding: var(--spacing-lg) var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    max-width: 400px;
    transform: translateX(500px);
    transition: transform var(--transition-base);
    z-index: 1000;
}

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

.toast-icon {
    font-size: 1.5rem;
}

.toast-message {
    flex: 1;
}

/* Toast Variants */
.toast.success {
    border-left: 4px solid var(--success-color);
}

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

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

/* ==========================================
   ANIMATIONS
   ========================================== */

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

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes bounce {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-10px);
    }
}

@keyframes float {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-15px);
    }
}

@keyframes spin {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}

@keyframes progressPulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.7;
    }
}

@keyframes scaleIn {
    from {
        transform: scale(0);
    }
    to {
        transform: scale(1);
    }
}

/* ==========================================
   RESPONSIVE DESIGN - MOBILE FIRST
   ========================================== */

/* Mobile Devices (320px - 767px) */
@media (max-width: 767px) {
    .container {
        padding: 0 var(--spacing-md);
    }
    
    .logo {
        font-size: 1.75rem;
    }
    
    .logo-icon {
        font-size: 2rem;
    }
    
    .tagline {
        font-size: 1rem;
    }
    
    .section-title {
        font-size: 1.5rem;
    }
    
    .section-description {
        font-size: 1rem;
    }
    
    .upload-area {
        padding: var(--spacing-2xl) var(--spacing-lg);
    }
    
    .upload-icon {
        font-size: 3rem;
    }
    
    .upload-title {
        font-size: 1.25rem;
    }
    
    .btn-large {
        padding: var(--spacing-md) var(--spacing-xl);
        font-size: 1rem;
        width: 100%;
    }
    
    .files-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .files-title {
        font-size: 1.25rem;
    }
    
    .file-item {
        padding: var(--spacing-md);
    }
    
    .file-icon {
        font-size: 2rem;
    }
    
    .file-name {
        font-size: 0.875rem;
    }
    
    .feature-card,
    .step {
        padding: var(--spacing-lg);
    }
    
    .step-arrow {
        display: none;
    }
    
    .steps-container {
        flex-direction: column;
    }
    
    .toast {
        right: var(--spacing-md);
        left: var(--spacing-md);
        bottom: var(--spacing-md);
        max-width: none;
    }
    
    .success-container,
    .progress-container {
        padding: var(--spacing-2xl) var(--spacing-lg);
    }
    
    .success-icon {
        font-size: 4rem;
    }
    
    .success-title {
        font-size: 1.5rem;
    }
}


nav li a {
    font-size: 1.5rem;
}



 footer {
            background: #2c3e50;
            color: white;
            padding: 3rem 5%;
        }

        .footer-content {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 2rem;
            margin-bottom: 2rem;
        }

        .footer-column h3 {
            font-size: 1.3rem;
            margin-bottom: 1.5rem;
            position: relative;
            padding-bottom: 10px;
        }

        .footer-column h3:after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 0;
            width: 50px;
            height: 3px;
            background: #3498db;
        }

        .footer-column p {
            margin-bottom: 1rem;
            color: #bdc3c7;
        }

        .footer-links {
            list-style: none;
        }

        .footer-links li {
            margin-bottom: 0.8rem;
        }

        .footer-links a {
            color: #bdc3c7;
            text-decoration: none;
            transition: color 0.3s;
        }

        .footer-links a:hover {
            color: #3498db;
        }

        .copyright {
            text-align: center;
            padding-top: 2rem;
            border-top: 1px solid rgba(255,255,255,0.1);
            color: #bdc3c7;
        }

/* Tablet Devices (768px - 1023px) */
@media (min-width: 768px) and (max-width: 1023px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Desktop Devices (1024px+) */
@media (min-width: 1024px) {
    .features-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

/* Touch-friendly interactions for mobile */
@media (hover: none) and (pointer: coarse) {
    .btn,
    .file-item,
    .feature-card,
    .step {
        -webkit-tap-highlight-color: transparent;
    }
    
    .file-drag-handle {
        font-size: 2rem;
    }
}

/* Reduced motion for accessibility */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}