:root {
    --primary-color: #4A90E2;
    --secondary-color: #50C878;
    --danger-color: #FF6B6B;
    --dark-color: #2C3E50;
    --light-color: #ECF0F1;
    --text-color: #333;
    --border-radius: 8px;
    --box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

/* Header Styles */
.header {
    background: white;
    box-shadow: var(--box-shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 10px;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: color 0.3s;
}

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

/* Hero Section */
.hero {
    text-align: center;
    padding: 4rem 2rem;
    color: white;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.2rem;
    opacity: 0.9;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-top: 2rem;
}

.stat {
    display: flex;
    flex-direction: column;
}

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

.stat-label {
    font-size: 0.9rem;
    opacity: 0.8;
}

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

/* Tool Section */
.tool-section {
    background: white;
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

.tool-header {
    text-align: center;
    margin-bottom: 2rem;
}

.tool-header i {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.tool-header h2 {
    font-size: 1.8rem;
    margin-bottom: 0.5rem;
    color: var(--dark-color);
}

.tool-header p {
    color: #666;
}

/* Upload Area */
.upload-area {
    border: 3px dashed #ddd;
    border-radius: 8px;
    padding: 3rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    margin-bottom: 1rem;
}

.upload-area:hover,
.upload-area.dragover {
    border-color: var(--primary-color);
    background: #f0f8ff;
}

.upload-area i {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.upload-area p {
    color: #666;
    margin-bottom: 1rem;
}

/* Buttons */
.btn-primary {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 1rem;
    transition: background 0.3s;
}

.btn-primary:hover {
    background: #357ABD;
}

.btn-convert {
    background: var(--secondary-color);
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 1.1rem;
    font-weight: bold;
    width: 100%;
    margin-top: 1rem;
    transition: all 0.3s;
}

.btn-convert:hover:not(:disabled) {
    background: #45B069;
    transform: translateY(-2px);
}

.btn-convert:disabled {
    background: #ccc;
    cursor: not-allowed;
}

/* Conversion Options */
.conversion-options,
.video-options,
.compression-level {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin: 1rem 0;
    flex-wrap: wrap;
}

.conversion-options label,
.video-options label,
.compression-level label {
    font-weight: 500;
}

select {
    padding: 0.5rem;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 1rem;
}

/* Quality Control */
.quality-control {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

input[type="range"] {
    width: 200px;
}

/* File List */
.file-list {
    margin: 1rem 0;
}

.file-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.5rem;
    background: #f8f9fa;
    border-radius: 4px;
    margin-bottom: 0.5rem;
}

.file-item i {
    color: var(--primary-color);
    font-size: 1.5rem;
}

.file-item .file-info {
    flex: 1;
}

.file-item .file-name {
    font-weight: 500;
}

.file-item .file-size {
    font-size: 0.9rem;
    color: #666;
}

.file-item .remove-file {
    color: var(--danger-color);
    cursor: pointer;
}

/* PDF Tabs */
.pdf-tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
    border-bottom: 2px solid #eee;
}

.tab-btn {
    padding: 0.8rem 1.5rem;
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    color: #666;
    transition: all 0.3s;
}

.tab-btn.active {
    color: var(--primary-color);
    border-bottom: 3px solid var(--primary-color);
}

.pdf-tab-content {
    display: none;
}

.pdf-tab-content.active {
    display: block;
}

/* Progress Bar */
.progress-bar {
    width: 100%;
    height: 10px;
    background: #eee;
    border-radius: 5px;
    overflow: hidden;
    margin: 1rem 0;
}

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

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 2000;
    justify-content: center;
    align-items: center;
}

.modal-content {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    text-align: center;
    min-width: 300px;
}

.spinner {
    border: 4px solid #f3f3f3;
    border-top: 4px solid var(--primary-color);
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
    margin: 0 auto 1rem;
}

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

/* Footer */
.footer {
    background: var(--dark-color);
    color: white;
    padding: 3rem 2rem 1rem;
    margin-top: 3rem;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

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

.footer-section a {
    display: block;
    color: #bbb;
    text-decoration: none;
    margin-bottom: 0.5rem;
    transition: color 0.3s;
}

.footer-section a:hover {
    color: white;
}

.footer-bottom {
    text-align: center;
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid #444;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav {
        flex-direction: column;
        gap: 1rem;
        padding: 1rem;
    }
    
    .nav-links {
        gap: 1rem;
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .hero h1 {
        font-size: 1.8rem;
    }
    
    .hero-stats {
        gap: 1.5rem;
    }
    
    .container {
        padding: 1rem;
    }
    
    .tool-section {
        padding: 1rem;
    }
    
    .upload-area {
        padding: 2rem 1rem;
    }
    
    .conversion-options,
    .video-options {
        flex-direction: column;
        align-items: flex-start;
    }
}