body{
    margin: 0;
    background-color: #141414;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    width: 100vw;
}

#calc_box {
    width: 350px;
    background-color: rgb(28, 27, 27);
    padding: 25px;
    border-radius: 15px;
}

#display_screen{
    width: 100%;
    height: 15vh;
    background-color: rgb(50, 49, 49);
    color: white;
    box-sizing: border-box;
    font-size: 23px;
    font-weight: bolder;
    padding: 10px;
    border-radius: 15px;
    border: none;
    margin-bottom: 25px;
}

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

.buttons button:hover{
    background:rgb(82, 81, 81);
}

.buttons button:not(.operator):hover{
    background:rgb(82, 81, 81);
}

.buttons button:not(.operator){
    height: 60px;
    background-color: rgb(50, 49, 49);
    border: none;
    border-radius: 10px;
    font-size: 20px;
    color: white;
    font-weight: 600;
}

#equals{
    grid-column: span 2;
    color: white;
    background-color: orange;
}

#equals:hover{
    background-color: rgb(255, 188, 63);
}
.operator{
    height: 60px;
    background-color: rgb(50, 49, 49);
    border: none;
    border-radius: 10px;
    font-size: 20px;
    font-weight: 600;
    color: orange
}

@keyframes bw_flash {
    0%   { background-color: black; color: white; }
    50%  { background-color: white; color: black; }
    100% { background-color: black; color: white; }
}

.change_bg {
    animation: bw_flash 0.75s infinite;
}