styles.css

body {
    display: grid;
    justify-content: center;
    align-items: center;
    height: 100vh;
    font-family: Arial, sans-serif;
    background-color: #f0f8ff;
    
}
.titulo{
    flex-shrink: 0;
    color: #000;
    text-align: center;
    font-size: 20px;
    font-style: normal;
    font-weight: 400;
    line-height: 54.5%;
    margin-top: 67px;
    margin-right: 410;

}
.calculadora {
    border: 1px solid #ffffff;
    width: 400px;
    border-radius: 10px;
    overflow: hidden;
    
}

.display {
    background-color: #000;
    color: #5FEB3E;
    padding: 10px 15px;
    font-size: 25px;
    text-align: right;
    border-radius: 10px;
   
}

.buttons {
    margin-top: 5px;
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    border: 1px solid #cccccc;
    border-radius: 10px;
    background-color: #f0f8ff;
}

button {
    margin-top: 5px;
    margin-left: 5px;
    margin-right: 5px;
    margin-bottom: 5px;
    padding: 30px;
    font-size: 20px;
    border-radius: 10px;
    background-color: #cccccc;
    cursor: pointer;
    
}

button:nth-child(4n-) {
    background-color: #f0f0f0;
}

button:hover {
    background-color: #e5e5e5;
}