:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --background-color: #f8fafc;
    --text-color: #1e293b;
    --border-color: #e2e8f0;
    --success-color: #22c55e;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

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

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

header h1 {
    font-size: 2.5rem;
    color: #2c3e50;
    margin-bottom: 1rem;
}

header p {
    color: #666;
    font-size: 1.1rem;
}

.process-steps {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    margin-bottom: 2rem;
}

.step {
    background: white;
    border-radius: 10px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    padding: 2rem;
}

.step-header {
    display: flex;
    align-items: center;
    margin-bottom: 1.5rem;
}

.step-number {
    background: #3498db;
    color: white;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    margin-right: 1rem;
}

.step h2 {
    color: #2c3e50;
    font-size: 1.5rem;
}

.mode-selection {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-bottom: 1.5rem;
}

.mode-option {
    background: #f8f9fa;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    padding: 1.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.mode-option:hover {
    border-color: #3498db;
    transform: translateY(-2px);
}

.mode-option.selected {
    border-color: #3498db;
    background: #ebf5ff;
}

.mode-option h3 {
    color: #2c3e50;
    margin-bottom: 0.5rem;
}

.mode-option p {
    color: #666;
    font-size: 0.9rem;
}

.upload-section {
    text-align: center;
}

.upload-box {
    border: 2px dashed #ccc;
    border-radius: 10px;
    padding: 2rem;
    margin-bottom: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.upload-box:hover {
    border-color: #3498db;
}

.upload-box.dragover {
    border-color: #3498db;
    background: #ebf5ff;
}

.upload-icon {
    width: 64px;
    height: 64px;
    margin-bottom: 1rem;
}

.upload-button {
    display: inline-block;
    background: #3498db;
    color: white;
    padding: 0.8rem 1.5rem;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s ease;
}

.upload-button:hover {
    background: #2980b9;
}

.settings-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

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

.setting-item label {
    font-weight: 500;
    color: #2c3e50;
}

.setting-item select {
    padding: 0.8rem;
    border: 1px solid #ddd;
    border-radius: 5px;
    font-size: 1rem;
}

.convert-button {
    background: #2ecc71;
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 5px;
    font-size: 1.1rem;
    cursor: pointer;
    transition: background 0.3s ease;
    width: 100%;
}

.convert-button:hover {
    background: #27ae60;
}

.convert-button:disabled {
    background: #95a5a6;
    cursor: not-allowed;
}

.remove-button {
    background: #e74c3c;
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s ease;
}

.remove-button:hover {
    background: #c0392b;
}

.progress-section {
    background: white;
    border-radius: 10px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.progress-bar {
    background: #f0f0f0;
    border-radius: 5px;
    height: 20px;
    margin: 1rem 0;
    overflow: hidden;
}

.progress {
    background: #3498db;
    height: 100%;
    width: 0;
    transition: width 0.3s ease;
}

.results-section {
    background: white;
    border-radius: 10px;
    padding: 2rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.results-controls {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.action-button {
    background: #3498db;
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s ease;
}

.action-button:hover {
    background: #2980b9;
}

.results-list {
    display: grid;
    gap: 1rem;
}

.result-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: #f8f9fa;
    border-radius: 5px;
}

.download-link {
    color: #3498db;
    text-decoration: none;
    font-weight: 500;
}

.download-link:hover {
    text-decoration: underline;
}

footer {
    text-align: center;
    margin-top: 3rem;
    color: #666;
}

.selected-file {
    background: #f8f9fa;
    padding: 1rem;
    border-radius: 5px;
    margin-top: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.hidden {
    display: none;
}

.back-button {
    background: #64748b;
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s ease;
    margin-top: 1rem;
    width: 100%;
}

.back-button:hover {
    background: #475569;
}

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

    header h1 {
        font-size: 2rem;
    }

    .upload-box {
        padding: 2rem;
    }

    .results-controls {
        flex-direction: column;
    }

    .action-button {
        width: 100%;
    }
}