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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 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: 28px;
}

.tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 30px;
}

.tab-btn {
    flex: 1;
    padding: 12px 20px;
    border: 2px solid #667eea;
    background: white;
    color: #667eea;
    border-radius: 10px;
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    transition: all 0.3s;
}

.tab-btn.active {
    background: #667eea;
    color: white;
}

.tab-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.3);
}

.panel {
    display: none;
}

.panel.active {
    display: block;
}

.upload-area {
    border: 3px dashed #ccc;
    border-radius: 15px;
    padding: 60px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    background: #f8f9fa;
}

.upload-area:hover {
    border-color: #667eea;
    background: #f0f2ff;
}

.upload-area.dragover {
    border-color: #667eea;
    background: #e8ebff;
    transform: scale(1.02);
}

.upload-icon {
    font-size: 64px;
    margin-bottom: 20px;
}

.upload-area p {
    color: #666;
    font-size: 18px;
    margin: 10px 0;
}

.file-limit {
    font-size: 14px !important;
    color: #999 !important;
}

.file-info {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    margin: 20px 0;
}

.file-info p {
    margin: 10px 0;
    color: #666;
}

.progress-container {
    margin: 30px 0;
}

.progress-bar {
    width: 100%;
    height: 30px;
    background: #e0e0e0;
    border-radius: 15px;
    overflow: hidden;
    margin: 15px 0;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #667eea 0%, #764ba2 100%);
    width: 0%;
    transition: width 0.3s;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: bold;
}

.progress-text {
    text-align: center;
    font-size: 18px;
    font-weight: bold;
    color: #667eea;
}

.result {
    text-align: center;
    padding: 20px;
}

.success-icon {
    width: 80px;
    height: 80px;
    background: #4caf50;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
    font-size: 48px;
    color: white;
}

.result h3 {
    color: #333;
    margin-bottom: 20px;
}

.key-display {
    background: #f8f9fa;
    padding: 25px;
    border-radius: 10px;
    margin: 20px 0;
}

.key-display p {
    color: #666;
    margin-bottom: 10px;
    font-size: 14px;
}

.key-code {
    font-size: 36px;
    font-weight: bold;
    color: #667eea;
    letter-spacing: 8px;
    margin: 15px 0;
    font-family: 'Courier New', monospace;
}

.copy-btn {
    background: #667eea;
    color: white;
    border: none;
    padding: 12px 30px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 16px;
    margin-top: 15px;
    transition: all 0.3s;
}

.copy-btn:hover {
    background: #5568d3;
    transform: translateY(-2px);
}

.expire-info {
    color: #999;
    font-size: 14px;
    margin: 20px 0;
}

.btn-secondary {
    background: #6c757d;
    color: white;
    border: none;
    padding: 12px 30px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 16px;
    transition: all 0.3s;
}

.btn-secondary:hover {
    background: #5a6268;
    transform: translateY(-2px);
}

.receive-form {
    text-align: center;
}

.receive-form h3 {
    color: #333;
    margin-bottom: 20px;
}

.key-input {
    width: 100%;
    padding: 15px;
    font-size: 24px;
    text-align: center;
    letter-spacing: 8px;
    border: 2px solid #ddd;
    border-radius: 10px;
    margin-bottom: 20px;
    font-family: 'Courier New', monospace;
    text-transform: uppercase;
}

.key-input:focus {
    outline: none;
    border-color: #667eea;
}

.btn-primary {
    width: 100%;
    background: #667eea;
    color: white;
    border: none;
    padding: 15px;
    border-radius: 10px;
    cursor: pointer;
    font-size: 18px;
    font-weight: 600;
    transition: all 0.3s;
}

.btn-primary:hover {
    background: #5568d3;
    transform: translateY(-2px);
}

.error-message {
    background: #ffebee;
    color: #c62828;
    padding: 15px;
    border-radius: 10px;
    margin-top: 20px;
    text-align: center;
}

@media (max-width: 600px) {
    .container {
        padding: 20px;
    }
    
    h1 {
        font-size: 24px;
    }
    
    .key-code {
        font-size: 28px;
        letter-spacing: 4px;
    }
}