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

:root {
    --primary: #667eea;
    --primary-dark: #5568d3;
    --secondary: #764ba2;
    --success: #10b981;
    --danger: #ef4444;
    --text: #1f2937;
    --bg: #f9fafb;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--text);
    background: var(--bg);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

header {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: white;
    padding: 3rem 0;
    text-align: center;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

header h1 {
    font-size: 3rem;
    margin-bottom: 0.5rem;
}

.tagline {
    font-size: 1.2rem;
    opacity: 0.95;
}

main {
    padding: 3rem 0;
}

.hero {
    text-align: center;
    margin-bottom: 3rem;
}

.hero h2 {
    color: var(--primary);
    font-size: 2rem;
    margin-bottom: 1rem;
}

.upload-section {
    background: white;
    padding: 3rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    margin-bottom: 3rem;
}

.upload-area {
    border: 3px dashed var(--primary);
    border-radius: 12px;
    padding: 4rem 2rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    margin-bottom: 2rem;
}

.upload-area:hover {
    background: #f0f4ff;
    border-color: var(--primary-dark);
}

.upload-area.dragover {
    background: #e0e7ff;
    border-color: var(--secondary);
    transform: scale(1.02);
}

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

.upload-area p {
    font-size: 1.1rem;
    color: var(--text);
    margin: 0.5rem 0;
}

.or {
    color: #9ca3af;
    font-size: 0.9rem;
}

#browseBtn {
    background: var(--primary);
    color: white;
    border: none;
    padding: 0.75rem 2rem;
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    margin-top: 1rem;
    transition: background 0.3s;
}

#browseBtn:hover {
    background: var(--primary-dark);
}

.file-info {
    margin-top: 1rem;
    font-weight: 600;
    color: var(--success);
}

.conversion-options {
    display: flex;
    gap: 1rem;
    align-items: center;
}

.conversion-options label {
    font-weight: 600;
    color: var(--text);
}

#formatSelect {
    flex: 1;
    padding: 0.75rem;
    border: 2px solid #e5e7eb;
    border-radius: 8px;
    font-size: 1rem;
}

#convertBtn {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: white;
    border: none;
    padding: 0.75rem 2rem;
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    transition: transform 0.2s;
    white-space: nowrap;
}

#convertBtn:hover:not(:disabled) {
    transform: translateY(-2px);
}

#convertBtn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.result-section {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    margin-bottom: 3rem;
}

.features {
    margin-top: 4rem;
}

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

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

.feature {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    transition: transform 0.3s;
}

.feature:hover {
    transform: translateY(-5px);
}

.feature h3 {
    color: var(--primary);
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

footer {
    background: var(--text);
    color: white;
    text-align: center;
    padding: 2rem 0;
    margin-top: 4rem;
}

footer a {
    color: var(--primary);
    text-decoration: none;
}

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

@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }
    
    .conversion-options {
        flex-direction: column;
    }
    
    #formatSelect {
        width: 100%;
    }
    
    .feature-grid {
        grid-template-columns: 1fr;
    }
}