* {
    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;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    padding: 40px;
    max-width: 600px;
    width: 100%;
}

h1 {
    text-align: center;
    color: #333;
    margin-bottom: 30px;
    font-size: 2em;
}

.upload-area {
    border: 3px dashed #667eea;
    border-radius: 15px;
    padding: 40px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    background: #f8f9ff;
    margin-bottom: 20px;
}

.upload-area:hover {
    background: #f0f2ff;
    border-color: #764ba2;
}

.upload-area.dragover {
    background: #e8ebff;
    border-color: #764ba2;
    transform: scale(1.02);
}

.upload-icon {
    font-size: 48px;
    margin-bottom: 15px;
}

.upload-text {
    color: #666;
    font-size: 16px;
    margin-bottom: 10px;
}

.file-input {
    display: none;
}

.file-info {
    margin: 20px 0;
    padding: 15px;
    background: #f8f9ff;
    border-radius: 10px;
    display: none;
}

.file-info.active {
    display: block;
}

.file-name {
    font-weight: bold;
    color: #333;
    margin-bottom: 10px;
}

.conversion-options {
    margin: 20px 0;
    display: none;
}

.conversion-options.active {
    display: block;
}

.option-group {
    margin-bottom: 15px;
}

label {
    display: block;
    margin-bottom: 8px;
    color: #333;
    font-weight: 500;
}

select {
    width: 100%;
    padding: 12px;
    border: 2px solid #ddd;
    border-radius: 8px;
    font-size: 16px;
    background: white;
    cursor: pointer;
    transition: border-color 0.3s;
}

select:focus {
    outline: none;
    border-color: #667eea;
}

.convert-btn {
    width: 100%;
    padding: 15px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    margin-top: 20px;
}

.convert-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 20px rgba(102, 126, 234, 0.4);
}

.convert-btn:active {
    transform: translateY(0);
}

.convert-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.download-area {
    margin-top: 20px;
    display: none;
}

.download-area.active {
    display: block;
}

.download-btn {
    width: 100%;
    padding: 15px;
    background: #28a745;
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    transition: background 0.3s;
    text-decoration: none;
    display: block;
    text-align: center;
}

.download-btn:hover {
    background: #218838;
}

.progress {
    width: 100%;
    height: 8px;
    background: #e0e0e0;
    border-radius: 4px;
    overflow: hidden;
    margin: 15px 0;
    display: none;
}

.progress.active {
    display: block;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, #667eea 0%, #764ba2 100%);
    width: 0%;
    transition: width 0.3s;
    animation: pulse 1.5s infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.7; }
}

.error {
    background: #fee;
    color: #c33;
    padding: 15px;
    border-radius: 10px;
    margin: 15px 0;
    display: none;
}

.error.active {
    display: block;
}