body {
    font-family: Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f4f4f4;
}

.calculator {
    background: #fff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

.screen {
    width: 80%;
    height: 50px;
    text-align: right;
    margin-bottom: 10px;
    padding: 10px;
    font-size: 24px;
    border: 1px solid #ccc;
    border-radius: 5px;
}

.btnRow {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-bottom: 10px;
}

.btn{
    padding: 15px;
    font-size: 18px;
    border: none;
    border-radius: 20px;
    background: #e0e0e0;
    cursor: pointer;
    transition: background-color 0.3s;
    text-align: center;
}

.btn:hover {
    background-color: #d4d4d4;
}