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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    text-align: center;
    margin-bottom: 40px;
    color: white;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    text-shadow: 0 2px 4px rgba(0,0,0,0.3);
}

header p {
    font-size: 1.1rem;
    opacity: 0.9;
}

main {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.upload-section {
    background: white;
    border-radius: 15px;
    padding: 30px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
    text-align: center;
}

.upload-area {
    border: 3px dashed #667eea;
    border-radius: 10px;
    padding: 40px 20px;
    transition: all 0.3s ease;
    cursor: pointer;
}

.upload-area:hover {
    border-color: #764ba2;
    background-color: #f8f9ff;
}

.upload-area.dragover {
    border-color: #764ba2;
    background-color: #f0f2ff;
    transform: scale(1.02);
}

.upload-icon {
    color: #667eea;
    margin-bottom: 15px;
}

.upload-content h3 {
    margin-bottom: 10px;
    color: #333;
}

.upload-content p {
    color: #666;
    margin-bottom: 20px;
}

.browse-btn {
    background: #667eea;
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 25px;
    cursor: pointer;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.browse-btn:hover {
    background: #764ba2;
    transform: translateY(-2px);
}

.file-info {
    margin-top: 20px;
}

.file-details {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: #f8f9ff;
    padding: 15px;
    border-radius: 8px;
    border: 1px solid #e1e5ee;
}

.file-name {
    font-weight: 500;
    color: #333;
}

.remove-btn {
    background: #ff4757;
    color: white;
    border: none;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.2rem;
    line-height: 1;
}

.convert-btn {
    width: 100%;
    background: #00b894;
    color: white;
    border: none;
    padding: 15px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1.1rem;
    font-weight: 600;
    margin-top: 20px;
    transition: all 0.3s ease;
}

.convert-btn:hover:not(:disabled) {
    background: #00a085;
    transform: translateY(-2px);
}

.convert-btn:disabled {
    background: #ccc;
    cursor: not-allowed;
    transform: none;
}

.loading-section,
.result-section,
.error-section {
    background: white;
    border-radius: 15px;
    padding: 40px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
    text-align: center;
}

.loading-spinner {
    border: 4px solid #f3f3f3;
    border-top: 4px solid #667eea;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

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

.loading-note {
    font-size: 0.9rem;
    color: #666;
    margin-top: 10px;
}

.success-icon,
.error-icon {
    margin-bottom: 20px;
}

.success-icon {
    color: #00b894;
}

.error-icon {
    color: #ff4757;
}

.download-btn,
.retry-btn {
    background: #667eea;
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 25px;
    cursor: pointer;
    font-size: 1rem;
    margin-top: 15px;
    transition: all 0.3s ease;
}

.download-btn:hover,
.retry-btn:hover {
    background: #764ba2;
    transform: translateY(-2px);
}

footer {
    text-align: center;
    margin-top: 40px;
    color: white;
    opacity: 0.8;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 15px;
    }
    
    header h1 {
        font-size: 2rem;
    }
    
    .upload-section,
    .loading-section,
    .result-section,
    .error-section {
        padding: 20px;
    }
}