.calculator-box {
        max-width: 800px;
        margin: 20px auto;
        padding: 20px;
        background: #404040;
        border-radius: 8px;
        box-shadow: 0 2px 4px rgba(0,0,0,0.1);
        color: white;
    }
    
    .calculator-box h3 {
        text-align: center;
        margin-bottom: 20px;
        color: white;
    }
    
    .calculator-box h4 {
        color: white;
        margin: 15px 0;
    }
    
    .calculator-form {
        display: flex;
        flex-direction: column;
        gap: 15px;
    }
    
    .input-group {
        display: flex;
        flex-direction: column;
        gap: 5px;
    }
    
    .input-group label {
        font-weight: bold;
        color: white;
    }
    
    .input-group input,
    .input-group select {
        padding: 8px;
        border: 1px solid #ddd;
        border-radius: 4px;
        font-size: 16px;
    }
    
    .result {
        margin-top: 20px;
        text-align: center;
        font-weight: bold;
    }
    
    #oil-amount,
    #new-speed,
    #displacement,
    #new-displacement {
        color: #f1111;
    }