body {
    background:white;           
    display: flex;
    justify-content: center;   
    align-items: center;      
    height: 100vh;             
    font-family: Arial, sans-serif;
    flex-direction: column;
    color: white;
}

h1 {
    margin-bottom: 20px;
    font-size: 2rem;
    color: orange;
    text-transform: uppercase;
    letter-spacing: 2px;
}
#Calculator {
    background: #222;          
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 0 15px rgba(255, 165, 0, 0.4);
}

#display {
    width: 100%;
    height: 50px;
    text-align: right;
    font-size: 1.5rem;
    margin-bottom: 15px;
    border: none;
    border-radius: 6px;
    padding: 0 10px;
    background: #333;
    color: white;
}
#keys {
    display: grid;
    grid-template-columns: repeat(4, 70px); 
    grid-gap: 10px;
}
#keys button {
    height: 60px;
    font-size: 1.2rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: 0.2s;
}
button.number {
    background: white;
    color: black;
}
button.operator {
    background: orange;
    color: white;
    font-weight: bold;
}
#keys button:hover {
    opacity: 0.85;
}