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

:root {
    --apple-blue: #007AFF;
    --apple-blue-hover: #0056B3;
    --apple-gray-1: #F2F2F7;
    --apple-gray-2: #E5E5EA;
    --apple-gray-3: #D1D1D6;
    --apple-gray-4: #C7C7CC;
    --apple-gray-5: #AEAEB2;
    --apple-gray-6: #8E8E93;
    --apple-text: #1D1D1F;
    --apple-text-secondary: #86868B;
    --apple-success: #30D158;
    --apple-warning: #FF9F0A;
    --apple-error: #FF3B30;
    --shadow-light: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-medium: 0 4px 20px rgba(0, 0, 0, 0.1);
    --shadow-heavy: 0 8px 40px rgba(0, 0, 0, 0.15);
    --border-radius: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #F5F7FA 0%, #C3CFE2 100%);
    color: var(--apple-text);
    min-height: 100vh;
    font-size: 16px;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.main-content {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 0;
}

/* Apple-style animations */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {

    0%,
    100% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.05);
    }
}

@keyframes shimmer {
    0% {
        transform: translateX(-100%);
    }

    100% {
        transform: translateX(100%);
    }
}

.animate-fade-in {
    animation: fadeInUp 0.6s ease-out forwards;
}

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

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

.text-primary {
    color: var(--apple-blue);
}

.text-success {
    color: var(--apple-success);
}

.text-secondary {
    color: var(--apple-text-secondary);
}

.mb-1 {
    margin-bottom: 8px;
}

.mb-2 {
    margin-bottom: 16px;
}

.mb-3 {
    margin-bottom: 24px;
}

.mb-4 {
    margin-bottom: 32px;
}

.mt-2 {
    margin-top: 16px;
}

.mt-3 {
    margin-top: 24px;
}

.p-3 {
    padding: 24px;
}

.hidden {
    display: none;
}

/* Responsive */
@media (max-width: 768px) {
    .container {
        padding: 0 16px;
    }

    .main-content {
        padding: 20px 0;
    }
}


.converter-container {
    max-width: 800px;
    margin: 0 auto;
}

.header .title {
    font-size: 3.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--apple-blue), #5856D6);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 8px;
    letter-spacing: -0.02em;
}

.header .subtitle {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--apple-text);
    margin-bottom: 8px;
}

.header .description {
    font-size: 1.1rem;
    color: var(--apple-text-secondary);
}

.converter-card {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    border-radius: 24px;
    padding: 48px;
    box-shadow: var(--shadow-heavy);
    border: 1px solid rgba(255, 255, 255, 0.2);
    position: relative;
    overflow: hidden;
}

.converter-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    animation: shimmer 3s infinite;
}

.section {
    opacity: 0;
    transform: translateY(20px);
    transition: var(--transition);
}

.section.active {
    opacity: 1;
    transform: translateY(0);
}

.step-header {
    text-align: center;
    margin-bottom: 32px;
}

.step-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    background: var(--apple-blue);
    color: white;
    border-radius: 50%;
    font-weight: 600;
    font-size: 1.2rem;
    margin-bottom: 16px;
}

.step-header h2 {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--apple-text);
}

.step-header p {
    color: var(--apple-text-secondary);
    font-size: 1.1rem;
}

.upload-area {
    border: 2px dashed var(--apple-gray-3);
    border-radius: var(--border-radius);
    padding: 64px 32px;
    text-align: center;
    transition: var(--transition);
    cursor: pointer;
    position: relative;
    margin-bottom: 24px;
    background: var(--apple-gray-1);
}

.upload-area:hover {
    border-color: var(--apple-blue);
    background: rgba(0, 122, 255, 0.02);
    transform: translateY(-2px);
}

.upload-area.dragover {
    border-color: var(--apple-blue);
    background: rgba(0, 122, 255, 0.05);
    transform: scale(1.02);
}

.upload-content .upload-icon {
    color: var(--apple-blue);
    margin-bottom: 16px;
}

.upload-content h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--apple-text);
}

.upload-content p {
    color: var(--apple-text-secondary);
    margin-bottom: 16px;
}

.browse-text {
    color: var(--apple-blue);
    font-weight: 500;
    cursor: pointer;
}

.file-types {
    font-size: 0.9rem;
    color: var(--apple-gray-6);
}

.file-preview {
    max-height: 300px;
    overflow-y: auto;
    margin-bottom: 24px;
    padding: 16px;
    background: var(--apple-gray-1);
    border-radius: var(--border-radius);
}

.quality-selector {
    margin-bottom: 24px;
    padding: 24px;
    background: var(--apple-gray-1);
    border-radius: var(--border-radius);
    border: 1px solid var(--apple-gray-2);
}

.quality-header {
    text-align: center;
    margin-bottom: 24px;
}

.quality-header h3 {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--apple-text);
}

.quality-header p {
    color: var(--apple-text-secondary);
    font-size: 0.95rem;
}

.quality-presets {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 12px;
    margin-bottom: 32px;
}

.quality-preset {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px;
    background: white;
    border: 2px solid var(--apple-gray-2);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    text-align: left;
}

.quality-preset:hover {
    border-color: var(--apple-blue);
    transform: translateY(-2px);
    box-shadow: var(--shadow-light);
}

.quality-preset.active {
    border-color: var(--apple-blue);
    background: rgba(0, 122, 255, 0.05);
}

.preset-icon {
    font-size: 1.5rem;
    width: 32px;
    text-align: center;
}

.preset-info {
    flex: 1;
}

.preset-name {
    font-weight: 600;
    color: var(--apple-text);
    margin-bottom: 2px;
}

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

.quality-slider-container {
    margin-bottom: 24px;
}

.quality-slider-container label {
    display: block;
    font-weight: 500;
    margin-bottom: 12px;
    color: var(--apple-text);
}

#quality-value {
    color: var(--apple-blue);
    font-weight: 600;
}

.quality-slider {
    width: 100%;
    height: 6px;
    border-radius: 3px;
    background: var(--apple-gray-2);
    outline: none;
    margin-bottom: 8px;
    -webkit-appearance: none;
    appearance: none;
}

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

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

.slider-labels {
    display: flex;
    justify-content: space-between;
    font-size: 0.85rem;
    color: var(--apple-text-secondary);
}

.quality-preview {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    padding: 16px;
    background: white;
    border-radius: 8px;
    border: 1px solid var(--apple-gray-2);
}

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

.preview-label {
    font-size: 0.85rem;
    color: var(--apple-text-secondary);
    margin-bottom: 4px;
}

.preview-value {
    font-weight: 600;
    color: var(--apple-blue);
    font-size: 1.1rem;
}

.file-item {
    display: flex;
    align-items: center;
    padding: 12px 0;
    border-bottom: 1px solid var(--apple-gray-2);
}

.file-item:last-child {
    border-bottom: none;
}

.file-icon {
    width: 40px;
    height: 40px;
    background: var(--apple-blue);
    color: white;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-right: 12px;
    font-weight: 600;
}

.file-info h4 {
    font-weight: 500;
    margin-bottom: 2px;
}

.file-info p {
    font-size: 0.9rem;
    color: var(--apple-text-secondary);
}

.btn-primary,
.btn-success,
.btn-secondary {
    width: 100%;
    padding: 16px 32px;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    position: relative;
    overflow: hidden;
}

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

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

.btn-primary:disabled {
    background: var(--apple-gray-4);
    color: var(--apple-gray-6);
    cursor: not-allowed;
}

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

.btn-success:hover {
    background: #28CD4C;
    transform: translateY(-2px);
    box-shadow: var(--shadow-medium);
}

.btn-secondary {
    background: var(--apple-gray-2);
    color: var(--apple-text);
}

.btn-secondary:hover {
    background: var(--apple-gray-3);
    transform: translateY(-2px);
}

.processing-container {
    max-width: 600px;
    margin: 0 auto;
}

.progress-list {
    margin-bottom: 32px;
}

.progress-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px;
    background: var(--apple-gray-1);
    border-radius: var(--border-radius);
    margin-bottom: 12px;
    transition: var(--transition);
}

.progress-item.completed {
    background: rgba(48, 209, 88, 0.1);
    color: var(--apple-success);
}

.progress-info {
    display: flex;
    align-items: center;
    gap: 12px;
}

.progress-status {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    font-weight: 600;
}

.progress-status.processing {
    background: var(--apple-blue);
    color: white;
    animation: pulse 2s infinite;
}

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

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

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--apple-gray-2);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 16px;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--apple-blue), #5856D6);
    width: 0%;
    transition: width 0.5s ease;
    border-radius: 4px;
}

.progress-text {
    font-weight: 500;
    color: var(--apple-text-secondary);
}

.conversion-results {
    background: var(--apple-gray-1);
    border-radius: var(--border-radius);
    padding: 24px;
    margin-bottom: 24px;
}

.result-summary {
    text-align: center;
    margin-bottom: 20px;
}

.result-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 16px;
    margin-top: 16px;
}

.stat-item {
    text-align: center;
    padding: 16px;
    background: white;
    border-radius: 8px;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--apple-blue);
}

.stat-label {
    font-size: 0.9rem;
    color: var(--apple-text-secondary);
    margin-top: 4px;
}

@media (max-width: 768px) {
    .converter-card {
        padding: 32px 24px;
    }

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

    .upload-area {
        padding: 48px 24px;
    }

    .step-header h2 {
        font-size: 1.5rem;
    }

    .quality-presets {
        grid-template-columns: 1fr;
    }
}