/* ==========================================
   CSS Variables & Reset
   ========================================== */
:root {
    --color-primary: #12b4b0;
    --color-primary-dark: #0e9894;
    --color-primary-light: #5fcbc8;
    --color-dark: #0C2C3D;
    --color-dark-lighter: #1a4255;
    --color-dark-light: #2d5670;
    --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-success: #10b981;
    --color-error: #ef4444;
    --color-warning: #f59e0b;

    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;

    --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);
    --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);

    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;

    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-gray-800);
    background: linear-gradient(135deg, var(--color-gray-50) 0%, var(--color-white) 100%);
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 2rem;
}

.hidden {
    display: none !important;
}

/* ==========================================
   Header
   ========================================== */
.header {
    background: var(--color-white);
    border-bottom: 1px solid var(--color-gray-200);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.logo img {
    display: block;
    height: 40px;
    width: auto;
}

.nav {
    display: flex;
    gap: 2rem;
    align-items: center;
}

.nav-link {
    color: var(--color-gray-700);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-fast);
    position: relative;
}

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

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--color-primary);
    transition: width var(--transition-base);
}

.nav-link:hover::after {
    width: 100%;
}

/* ==========================================
   Hero Section
   ========================================== */
.hero {
    padding: 4rem 0 6rem;
}

.hero-content {
    max-width: 900px;
    margin: 0 auto;
    text-align: center;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 800;
    color: var(--color-dark);
    margin-bottom: 1rem;
    letter-spacing: -0.02em;
    line-height: 1.1;
}

.hero-subtitle {
    font-size: 1.375rem;
    color: var(--color-gray-600);
    margin-bottom: 3rem;
    font-weight: 400;
}

/* ==========================================
   Upload Area
   ========================================== */
.upload-wrapper {
    margin-bottom: 3rem;
}

.upload-area {
    background: var(--color-white);
    border: 3px dashed var(--color-gray-300);
    border-radius: var(--radius-2xl);
    padding: 4rem 2rem;
    transition: all var(--transition-base);
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.upload-area:hover {
    border-color: var(--color-primary);
    background: var(--color-gray-50);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.upload-area.drag-over {
    border-color: var(--color-primary);
    background: linear-gradient(135deg, rgba(18, 180, 176, 0.05) 0%, rgba(18, 180, 176, 0.1) 100%);
    transform: scale(1.02);
}

.upload-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.upload-icon {
    width: 80px;
    height: 80px;
    color: var(--color-primary);
    margin-bottom: 0.5rem;
}

.upload-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-dark);
}

.upload-text {
    font-size: 1.125rem;
    color: var(--color-gray-500);
}

.upload-limit {
    font-size: 0.875rem;
    color: var(--color-gray-400);
    margin-top: 0.5rem;
}

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

/* ==========================================
   File Preview
   ========================================== */
.file-preview {
    background: var(--color-white);
    border-radius: var(--radius-xl);
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-md);
}

.file-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
    margin-bottom: 1rem;
    transition: all var(--transition-fast);
}

.file-item:hover {
    background: var(--color-gray-100);
}

.file-item:last-child {
    margin-bottom: 0;
}

.file-thumbnail {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-md);
    object-fit: cover;
    background: var(--color-white);
    border: 2px solid var(--color-gray-200);
}

.file-info {
    flex: 1;
}

.file-name {
    font-weight: 600;
    color: var(--color-dark);
    margin-bottom: 0.25rem;
    font-size: 0.95rem;
}

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

.file-remove {
    background: var(--color-error);
    color: var(--color-white);
    border: none;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    font-size: 1.25rem;
    line-height: 1;
}

.file-remove:hover {
    background: #dc2626;
    transform: scale(1.1);
}

/* ==========================================
   Format Selector
   ========================================== */
.format-selector {
    background: var(--color-white);
    border-radius: var(--radius-xl);
    padding: 2.5rem;
    box-shadow: var(--shadow-lg);
}

.format-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-dark);
    margin-bottom: 1.5rem;
    text-align: center;
}

.format-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    gap: 0.75rem;
    margin-bottom: 2rem;
}

.format-btn {
    background: var(--color-gray-50);
    border: 2px solid var(--color-gray-200);
    border-radius: var(--radius-lg);
    padding: 1rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: 0.25rem;
}

.format-btn:hover {
    border-color: var(--color-primary);
    background: var(--color-white);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.format-btn.selected {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    border-color: var(--color-primary);
    color: var(--color-white);
    transform: scale(1.05);
    box-shadow: var(--shadow-lg);
}

.format-name {
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--color-dark);
}

.format-btn.selected .format-name {
    color: var(--color-white);
}

.format-desc {
    font-size: 0.75rem;
    color: var(--color-gray-500);
    line-height: 1.3;
}

.format-btn.selected .format-desc {
    color: rgba(255, 255, 255, 0.9);
}

/* ==========================================
   Convert Button
   ========================================== */
.convert-btn {
    width: 100%;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: var(--color-white);
    border: none;
    border-radius: var(--radius-xl);
    padding: 1.25rem 2rem;
    font-size: 1.125rem;
    font-weight: 700;
    cursor: pointer;
    transition: all var(--transition-base);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    box-shadow: var(--shadow-lg);
}

.convert-btn:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: var(--shadow-xl);
}

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

.convert-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-icon {
    width: 24px;
    height: 24px;
}

.btn-secondary {
    background: var(--color-white);
    color: var(--color-primary);
    border: 2px solid var(--color-primary);
    border-radius: var(--radius-xl);
    padding: 1rem 2rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    display: inline-block;
}

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

/* ==========================================
   Conversion Progress
   ========================================== */
.conversion-progress {
    background: var(--color-white);
    border-radius: var(--radius-xl);
    padding: 2rem;
    box-shadow: var(--shadow-lg);
}

.progress-item {
    margin-bottom: 1.5rem;
}

.progress-item:last-child {
    margin-bottom: 0;
}

.progress-info {
    display: flex;
    justify-content: space-between;
    margin-bottom: 0.75rem;
}

.progress-filename {
    font-weight: 600;
    color: var(--color-dark);
}

.progress-status {
    font-weight: 600;
    color: var(--color-primary);
}

.progress-bar {
    height: 8px;
    background: var(--color-gray-200);
    border-radius: var(--radius-xl);
    overflow: hidden;
}

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

/* ==========================================
   Download Area
   ========================================== */
.download-area {
    background: var(--color-white);
    border-radius: var(--radius-xl);
    padding: 3rem 2rem;
    text-align: center;
    box-shadow: var(--shadow-lg);
}

.download-success {
    margin-bottom: 2rem;
}

.success-icon {
    width: 80px;
    height: 80px;
    color: var(--color-success);
    margin: 0 auto 1rem;
}

.success-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--color-dark);
}

.download-links {
    margin-bottom: 2rem;
}

.download-link {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1.25rem;
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
    margin-bottom: 0.75rem;
    text-decoration: none;
    transition: all var(--transition-fast);
}

.download-link:hover {
    background: var(--color-gray-100);
    transform: translateX(4px);
}

.download-info {
    text-align: left;
}

.download-name {
    font-weight: 600;
    color: var(--color-dark);
    margin-bottom: 0.25rem;
}

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

.download-icon {
    width: 24px;
    height: 24px;
    color: var(--color-primary);
}

/* ==========================================
   Stats
   ========================================== */
.stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    margin-top: 3rem;
}

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

.stat-number {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--color-primary);
    margin-bottom: 0.5rem;
    line-height: 1;
}

.stat-label {
    font-size: 0.875rem;
    color: var(--color-gray-600);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 600;
}

/* ==========================================
   Features Section
   ========================================== */
.features {
    padding: 5rem 0;
    background: var(--color-white);
}

.section-title {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--color-dark);
    text-align: center;
    margin-bottom: 3rem;
    letter-spacing: -0.02em;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.feature-card {
    padding: 2rem;
    border-radius: var(--radius-xl);
    background: var(--color-gray-50);
    transition: all var(--transition-base);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    background: var(--color-white);
}

.feature-icon {
    width: 48px;
    height: 48px;
    padding: 12px;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    border-radius: var(--radius-lg);
    color: var(--color-white);
    margin-bottom: 1.5rem;
}

.feature-icon svg {
    width: 100%;
    height: 100%;
}

.feature-title {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-dark);
    margin-bottom: 0.75rem;
}

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

/* ==========================================
   Formats Section
   ========================================== */
.formats-section {
    padding: 5rem 0;
    background: linear-gradient(135deg, var(--color-dark) 0%, var(--color-dark-lighter) 100%);
}

.formats-section .section-title {
    color: var(--color-white);
}

.formats-list {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    justify-content: center;
    max-width: 800px;
    margin: 0 auto;
}

.format-tag {
    padding: 0.75rem 1.5rem;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-xl);
    color: var(--color-white);
    font-weight: 600;
    font-size: 0.95rem;
    transition: all var(--transition-fast);
    backdrop-filter: blur(10px);
}

.format-tag:hover {
    background: rgba(18, 180, 176, 0.3);
    border-color: var(--color-primary);
    transform: translateY(-2px);
}

/* ==========================================
   Footer
   ========================================== */
.footer {
    background: var(--color-dark);
    color: var(--color-white);
    padding: 4rem 0 2rem;
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 3fr;
    gap: 4rem;
    margin-bottom: 3rem;
}

.footer-brand img {
    height: 32px;
    margin-bottom: 1rem;
    filter: brightness(0) invert(1);
}

.footer-tagline {
    color: rgba(255, 255, 255, 0.7);
    font-size: 0.95rem;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
}

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

.footer-title {
    font-size: 0.875rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.5rem;
}

.footer-link {
    color: rgba(255, 255, 255, 0.7);
    text-decoration: none;
    font-size: 0.95rem;
    transition: color var(--transition-fast);
}

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

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.5);
    font-size: 0.875rem;
}

/* ==========================================
   Responsive Design
   ========================================== */
@media (max-width: 768px) {
    .container {
        padding: 0 1.5rem;
    }

    .nav {
        gap: 1rem;
    }

    .nav-link {
        font-size: 0.875rem;
    }

    .hero {
        padding: 2rem 0 4rem;
    }

    .hero-title {
        font-size: 2.5rem;
    }

    .hero-subtitle {
        font-size: 1.125rem;
    }

    .upload-area {
        padding: 3rem 1.5rem;
    }

    .upload-icon {
        width: 60px;
        height: 60px;
    }

    .upload-title {
        font-size: 1.25rem;
    }

    .format-grid {
        grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
        gap: 0.5rem;
    }

    .format-btn {
        padding: 0.75rem;
    }

    .format-name {
        font-size: 1rem;
    }

    .stats {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }

    .stat-number {
        font-size: 2rem;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .footer-content {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .footer-links {
        grid-template-columns: 1fr;
    }

    .section-title {
        font-size: 2rem;
    }
}

/* ==========================================
   Animations
   ========================================== */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.05);
    }
}

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

.animate-fade-in {
    animation: fadeIn 0.5s ease-out;
}

.animate-pulse {
    animation: pulse 2s ease-in-out infinite;
}

.animate-spin {
    animation: spin 1s linear infinite;
}

/* ==========================================
   Utility Classes
   ========================================== */
.text-center {
    text-align: center;
}

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }