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

body {
    background-color: #333;
    display: flex;
    align-items: center;
    justify-content:center;
    padding: 3em;
}

#calc{
   width: 400px;
   padding: 0.5em;
   background-color: #c4c4c4;
   color: black;
   display: flex;
   flex-direction: column;
}

h3{
    font-size: 0.8em;
    font-weight: 300px;
    color: #666;
}
    

#operations{
    text-align: right;
}

#current-operation{
    min-height: 1.6em;
    padding: 0.2em;
    overflow-wrap: break-word;
}

#current-operation{
    font-size: 3em;
    font-weight: 700;
}

#buttons-container{
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    gap: 3px;
}

#buttons-container button {
    border: 1px solid transparent;
    border-radius: 0;
    height: 4em;
    font-size: 1.2em;
    background-color: #dbdbdb;
    cursor: pointer;
}

#buttons-container.number{
    background-color: #f3f3f3;
}

#buttons-container button:hover{
    background-color: #bababa;
    border-color: #999;
}

#buttons-container #equal-btr{
    grid-column: span 2;
    background-color: #9ecee4;
}

#buttons-container #equal-btr:hover{
   background-color: #2a4c5c;
}