style.css

@import url('https://fonts.googleapis.com/css2?family=Playwrite+DE+Grund:wght@100..400&display=swap');

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

html{
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: "Playwrite DE Grund", cursive;
}

.body {
    max-width: 500px;
    overflow: hidden;
    margin-top: 80px;
    border-radius: 20px;
    background-color: rgba(0, 0, 0, 0.782);
    padding: 15px;
}

.screen {
    width: 100%;
    padding: 20px;
    border: none;
    border-radius: 20px;
    text-align: right;
    font-family: "Playwrite DE Grund", cursive;
    font-weight: bold;
    font-size: 1.5rem;
    background-color: rgba(0, 0, 0, 0.236);
    color: white;
    outline: none;

}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    width: 75px;
    height: 75px;
    border-radius: 50px;
    border: none;
    font-family: "Playwrite DE Grund", cursive;
    font-weight: bold;
    font-size: 1rem;
    transition: transform 0.2s ease-in-out;
}

.btn:hover{
    transform: scale(1.1);
}

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

.normal-btn {
    background-color: rgb(181, 181, 181);
}

.normal-btn:active {
    background-color: rgba(181, 181, 181, 0.637);

}

.operations {
    background-color: rgb(0, 213, 255);
}

.operations:active {
    background-color: rgb(0, 213, 255, 0.637);
}