/* CSS Variables */
:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --secondary-color: #64748b;
    --secondary-hover: #475569;
    --success-color: #10b981;
    --error-color: #ef4444;
    --background: #f8fafc;
    --surface: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --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);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
}

/* Reset & Base */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* App Container */
.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    text-align: center;
    padding: 2rem 1rem;
    background: var(--surface);
    border-bottom: 1px solid var(--border-color);
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.logo-icon {
    width: 48px;
    height: 48px;
    object-fit: contain;
}

.header h1 {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-primary);
}

.tagline {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* Main Content */
.main-content {
    flex: 1;
    padding: 2rem 1rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

/* Upload Section */
.upload-section {
    max-width: 600px;
    margin: 0 auto;
}

.upload-area {
    background: var(--surface);
    border: 2px dashed var(--border-color);
    border-radius: var(--radius-lg);
    padding: 3rem 2rem;
    text-align: center;
    transition: all 0.2s ease;
    cursor: pointer;
}

.upload-area:hover,
.upload-area.drag-over {
    border-color: var(--primary-color);
    background: #f0f0ff;
}

.upload-icon {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.upload-area h2 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.upload-area p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
    text-decoration: none;
}

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

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

.btn-secondary {
    background: var(--surface);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--background);
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.125rem;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* Converter Section */
.converter-section {
    max-width: 900px;
    margin: 0 auto;
}

.pdf-info {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 1rem;
    background: var(--surface);
    padding: 1rem 1.5rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    margin-bottom: 1.5rem;
}

.file-details {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.file-icon {
    color: var(--primary-color);
}

#fileName {
    font-weight: 500;
    word-break: break-all;
}

.page-count {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* Settings Grid */
.settings-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-bottom: 1.5rem;
}

.settings-card {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
}

.settings-card h3 {
    font-size: 1rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

/* Page Selection */
.page-selection {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.radio-option {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    cursor: pointer;
}

.radio-option input[type="radio"] {
    width: 18px;
    height: 18px;
    accent-color: var(--primary-color);
}

.radio-label {
    font-size: 0.95rem;
}

.range-input {
    margin-left: 1.75rem;
    margin-top: 0.5rem;
}

.range-input input {
    width: 100%;
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
}

.range-input input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.range-input small {
    display: block;
    margin-top: 0.25rem;
    color: var(--text-secondary);
    font-size: 0.8rem;
}

/* Quality Settings */
.quality-settings {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.setting-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.setting-group label {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.setting-group select,
.setting-group input[type="range"] {
    width: 100%;
}

.setting-group select {
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    background: var(--surface);
    cursor: pointer;
}

.setting-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.setting-group input[type="range"] {
    height: 6px;
    -webkit-appearance: none;
    appearance: none;
    background: var(--border-color);
    border-radius: 3px;
    cursor: pointer;
}

.setting-group input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    background: var(--primary-color);
    border-radius: 50%;
    cursor: pointer;
}

/* Thumbnails Section */
.thumbnails-section {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    margin-bottom: 1.5rem;
}

.thumbnails-section h3 {
    margin-bottom: 1rem;
}

.thumbnail-actions {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

#selectedCount {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-left: auto;
}

.thumbnails-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 1rem;
    max-height: 400px;
    overflow-y: auto;
    padding: 0.5rem;
}

.thumbnail-item {
    position: relative;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    overflow: hidden;
    cursor: pointer;
    transition: all 0.2s ease;
    aspect-ratio: 3/4;
    background: #f1f5f9;
}

.thumbnail-item:hover {
    border-color: var(--primary-color);
}

.thumbnail-item.selected {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(99, 102, 241, 0.3);
}

.thumbnail-item canvas {
    width: 100%;
    height: 100%;
    object-fit: contain;
}

.thumbnail-overlay {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(0, 0, 0, 0.7);
    color: white;
    padding: 0.25rem 0.5rem;
    font-size: 0.75rem;
    text-align: center;
}

.thumbnail-check {
    position: absolute;
    top: 0.5rem;
    right: 0.5rem;
    width: 24px;
    height: 24px;
    background: var(--primary-color);
    border-radius: 50%;
    display: none;
    align-items: center;
    justify-content: center;
    color: white;
}

.thumbnail-item.selected .thumbnail-check {
    display: flex;
}

/* Convert Section */
.convert-section {
    text-align: center;
    margin-bottom: 1.5rem;
}

.btn-loading {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.spinner {
    width: 20px;
    height: 20px;
    animation: spin 1s linear infinite;
}

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

/* Progress Section */
.progress-section {
    max-width: 500px;
    margin: 0 auto 1.5rem;
}

.progress-bar {
    height: 8px;
    background: var(--border-color);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 0.75rem;
}

.progress-fill {
    height: 100%;
    background: var(--primary-color);
    border-radius: 4px;
    transition: width 0.3s ease;
    width: 0%;
}

.progress-text {
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Results Section */
.results-section {
    max-width: 1000px;
    margin: 0 auto;
}

.results-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.results-header h2 {
    font-size: 1.25rem;
}

.results-actions {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 1.5rem;
}

.result-item {
    background: var(--surface);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: box-shadow 0.2s ease;
}

.result-item:hover {
    box-shadow: var(--shadow-md);
}

.result-preview {
    aspect-ratio: 3/4;
    background: #f1f5f9;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.result-preview img {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
}

.result-info {
    padding: 1rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 0.5rem;
}

.result-name {
    font-size: 0.9rem;
    font-weight: 500;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.result-download {
    flex-shrink: 0;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--primary-color);
    color: white;
    border-radius: var(--radius-sm);
    text-decoration: none;
    transition: background 0.2s ease;
}

.result-download:hover {
    background: var(--primary-hover);
}

/* Footer */
.footer {
    text-align: center;
    padding: 1.5rem 1rem;
    background: var(--surface);
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}

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

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

.footer a:hover {
    text-decoration: underline;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .header {
        padding: 1.5rem 1rem;
    }

    .header h1 {
        font-size: 1.5rem;
    }

    .logo-icon {
        width: 40px;
        height: 40px;
    }

    .main-content {
        padding: 1.5rem 1rem;
    }

    .upload-area {
        padding: 2rem 1.5rem;
    }

    .upload-icon svg {
        width: 48px;
        height: 48px;
    }

    .pdf-info {
        flex-direction: column;
        align-items: flex-start;
    }

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

    .thumbnails-grid {
        grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    }

    .results-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .results-actions {
        width: 100%;
    }

    .results-actions .btn {
        flex: 1;
    }

    .results-grid {
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
        gap: 1rem;
    }

    #selectedCount {
        margin-left: 0;
        width: 100%;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .upload-area h2 {
        font-size: 1.1rem;
    }

    .btn-large {
        width: 100%;
        padding: 0.875rem 1.5rem;
    }

    .thumbnail-actions {
        justify-content: center;
    }

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

/* Utility Classes */
.hidden {
    display: none !important;
}

/* Loading State for Thumbnails */
.thumbnail-item.loading {
    display: flex;
    align-items: center;
    justify-content: center;
}

.thumbnail-item.loading::after {
    content: '';
    width: 24px;
    height: 24px;
    border: 2px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}