:root {
    /* Background colors */
    --bg-app: #0C0C0D;
    --bg-card: #111113;
    --bg-section: #18181B;
    --bg-drop-zone: #0F0F10;
    --bg-drop-zone-hover: #0D1117;
    
    /* Border colors */
    --border-card: #1C1C1F;
    --border-subtle: #3E3E42;
    --border-accent: #0090FF;
    --border-accent-alpha: #0090FF20;
    
    /* Text colors */
    --text-primary: #EEEEEF;
    --text-secondary: #B4B4B6;
    --text-muted: #9B9B9D;
    
    /* Accent colors */
    --accent-primary: #0090FF;
    --accent-primary-hover: #3B9EFF;
    
    /* Status colors */
    --success-bg: #0D1B0D;
    --success-border: #30A46C;
    --success-text: #46A758;
    
    --error-bg: #1C1618;
    --error-border: #E5484D;
    --error-text: #F2555A;
}

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

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

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

header {
    text-align: center;
    margin-bottom: 40px;
    color: var(--text-primary);
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
}

.subtitle {
    font-size: 1.2rem;
    color: var(--text-secondary);
    font-weight: 300;
}

main {
    background: var(--bg-card);
    border: 1px solid var(--border-card);
    border-radius: 12px;
    padding: 40px;
    margin-bottom: 20px;
}

.converter-section {
    margin-bottom: 60px;
}

.drop-zone {
    border: 2px dashed var(--border-subtle);
    border-radius: 8px;
    padding: 60px 20px;
    text-align: center;
    transition: all 0.3s ease;
    cursor: pointer;
    background: var(--bg-drop-zone);
    position: relative;
}

.drop-zone:hover,
.drop-zone.drag-over {
    border-color: var(--border-accent);
    background: var(--bg-drop-zone-hover);
    transform: translateY(-1px);
    box-shadow: 0 0 0 1px var(--border-accent-alpha);
}

.drop-content {
    pointer-events: none;
}

.upload-icon {
    color: var(--text-muted);
    margin-bottom: 20px;
}

.drop-zone h2 {
    font-size: 1.8rem;
    margin-bottom: 10px;
    color: var(--text-primary);
    font-weight: 600;
}

.drop-zone p {
    color: var(--text-secondary);
    font-size: 1.1rem;
    margin-bottom: 10px;
}

.browse-button {
    background: none;
    border: none;
    color: var(--accent-primary);
    text-decoration: underline;
    cursor: pointer;
    font-size: inherit;
    font-weight: 600;
    transition: color 0.2s ease;
}

.browse-button:hover {
    color: var(--accent-primary-hover);
}

.drop-zone small {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.conversion-status {
    background: var(--bg-drop-zone);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    padding: 40px;
    text-align: center;
    margin-top: 20px;
}

.status-content h3 {
    font-size: 1.5rem;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.status-content p {
    color: var(--text-secondary);
    margin-bottom: 20px;
}

.progress-indicator {
    margin-bottom: 20px;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 4px solid var(--border-subtle);
    border-top: 4px solid var(--accent-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.file-info {
    background: var(--bg-section);
    border: 1px solid var(--border-subtle);
    border-radius: 6px;
    padding: 15px;
    margin-top: 15px;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.features {
    margin-bottom: 40px;
}

.features h2 {
    text-align: center;
    font-size: 2rem;
    margin-bottom: 30px;
    color: var(--text-primary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.feature {
    text-align: center;
    padding: 20px;
}

.feature h3 {
    font-size: 1.2rem;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.feature p {
    color: var(--text-secondary);
    line-height: 1.5;
}

.about {
    background: var(--bg-section);
    border: 1px solid var(--border-subtle);
    padding: 30px;
    border-radius: 8px;
    margin-bottom: 20px;
}

.about h2 {
    font-size: 1.5rem;
    margin-bottom: 15px;
    color: var(--text-primary);
}

.about p {
    color: var(--text-secondary);
    line-height: 1.7;
    font-size: 1rem;
}

footer {
    text-align: center;
    color: var(--text-muted);
    font-size: 0.9rem;
}

.success-message {
    background: var(--success-bg);
    border: 1px solid var(--success-border);
    color: var(--success-text);
}

.error-message {
    background: var(--error-bg);
    border: 1px solid var(--error-border);
    color: var(--error-text);
}

.download-button {
    background: var(--accent-primary);
    color: #FFFFFF;
    border: none;
    padding: 12px 24px;
    border-radius: 6px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s ease;
    margin-top: 15px;
}

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

/* How-to Guide Section */
.how-to-guide {
    margin-bottom: 40px;
}

.how-to-guide h2 {
    font-size: 1.8rem;
    margin-bottom: 30px;
    text-align: center;
    color: var(--text-primary);
}

.steps-container {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.step {
    display: flex;
    gap: 20px;
    align-items: flex-start;
    background: var(--bg-section);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    padding: 25px;
    transition: all 0.2s ease;
}

.step:hover {
    border-color: var(--border-accent);
    transform: translateX(5px);
}

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

.step-content h3 {
    font-size: 1.2rem;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.step-content p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Comparison Table Section */
.comparison {
    margin-bottom: 40px;
}

.comparison h2 {
    font-size: 1.8rem;
    margin-bottom: 30px;
    text-align: center;
    color: var(--text-primary);
}

.comparison-table {
    background: var(--bg-section);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    overflow: hidden;
}

.comparison-row {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    border-bottom: 1px solid var(--border-subtle);
}

.comparison-row:last-child {
    border-bottom: none;
}

.comparison-row.header {
    background: var(--bg-drop-zone);
}

.comparison-row.header .comparison-cell {
    font-weight: 700;
    color: var(--text-primary);
    font-size: 1.05rem;
}

.comparison-cell {
    padding: 15px 20px;
    color: var(--text-secondary);
    border-right: 1px solid var(--border-subtle);
}

.comparison-cell:last-child {
    border-right: none;
}

.comparison-cell.highlight {
    color: var(--accent-primary);
    font-weight: 600;
}

.comparison-summary {
    margin-top: 20px;
    padding: 20px;
    background: var(--bg-section);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    color: var(--text-secondary);
    line-height: 1.7;
}

/* Use Cases Section */
.use-cases {
    margin-bottom: 40px;
}

.use-cases h2 {
    font-size: 1.8rem;
    margin-bottom: 30px;
    text-align: center;
    color: var(--text-primary);
}

.use-cases-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 25px;
}

.use-case {
    background: var(--bg-section);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    padding: 25px;
    text-align: center;
    transition: all 0.2s ease;
}

.use-case:hover {
    border-color: var(--border-accent);
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(0, 144, 255, 0.15);
}

.use-case-icon {
    font-size: 2.5rem;
    margin-bottom: 15px;
}

.use-case h3 {
    font-size: 1.1rem;
    margin-bottom: 10px;
    color: var(--text-primary);
    font-weight: 600;
}

.use-case p {
    color: var(--text-secondary);
    line-height: 1.6;
    font-size: 0.95rem;
}

/* Support Section (Buy Me a Coffee) */
.support-section {
    margin-bottom: 40px;
    background: linear-gradient(135deg, var(--bg-section) 0%, var(--bg-drop-zone) 100%);
    border: 1px solid var(--border-accent);
    border-radius: 12px;
    padding: 30px;
    position: relative;
    overflow: hidden;
}

.support-section::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(0, 144, 255, 0.05) 0%, transparent 70%);
    pointer-events: none;
}

.support-content {
    display: flex;
    align-items: center;
    gap: 25px;
    position: relative;
    z-index: 1;
}

.support-icon {
    font-size: 3rem;
    flex-shrink: 0;
    animation: float 3s ease-in-out infinite;
}

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

.support-text {
    flex: 1;
}

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

.support-text p {
    color: var(--text-secondary);
    line-height: 1.6;
    margin: 0;
}

.support-button-wrapper {
    flex-shrink: 0;
}

.coffee-button {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    background: #FFDD00;
    color: #000000;
    padding: 12px 24px;
    border-radius: 8px;
    font-weight: 600;
    font-size: 1rem;
    text-decoration: none;
    transition: all 0.3s ease;
    box-shadow: 0 4px 12px rgba(255, 221, 0, 0.3);
}

.coffee-button:hover {
    background: #FFE84D;
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(255, 221, 0, 0.4);
}

.coffee-button:active {
    transform: translateY(0);
}

.coffee-button svg {
    width: 20px;
    height: 20px;
}

/* FAQ Section */
.faq {
    margin-bottom: 20px;
}

.faq h2 {
    font-size: 1.8rem;
    margin-bottom: 30px;
    text-align: center;
    color: var(--text-primary);
}

.faq-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 25px;
}

.faq-item {
    background: var(--bg-section);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    padding: 25px;
    transition: all 0.2s ease;
}

.faq-item:hover {
    border-color: var(--border-accent);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 144, 255, 0.1);
}

.faq-item h3 {
    font-size: 1.1rem;
    margin-bottom: 12px;
    color: var(--text-primary);
    font-weight: 600;
}

.faq-item p {
    color: var(--text-secondary);
    line-height: 1.6;
    font-size: 0.95rem;
}

/* Responsive design */
@media (max-width: 768px) {
    .container {
        padding: 15px;
    }

    header h1 {
        font-size: 2rem;
    }

    main {
        padding: 20px;
    }

    .drop-zone {
        padding: 40px 15px;
    }

    .drop-zone h2 {
        font-size: 1.5rem;
    }

    .features-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }

    .faq-grid {
        grid-template-columns: 1fr;
        gap: 15px;
    }

    .step {
        flex-direction: column;
        text-align: center;
    }

    .step-number {
        margin: 0 auto;
    }

    .comparison-row {
        grid-template-columns: 1fr;
    }

    .comparison-cell {
        border-right: none;
        border-bottom: 1px solid var(--border-subtle);
    }

    .comparison-cell:last-child {
        border-bottom: none;
    }

    .comparison-row.header .comparison-cell:not(:first-child) {
        display: none;
    }

    .use-cases-grid {
        grid-template-columns: 1fr;
    }

    .support-content {
        flex-direction: column;
        text-align: center;
        gap: 20px;
    }

    .support-section {
        padding: 25px 20px;
    }

    .support-icon {
        font-size: 2.5rem;
    }

    .coffee-button {
        width: 100%;
        justify-content: center;
    }
}