*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
.container{
    width: 316px;
    margin: 0 auto;
}
h1{
    text-align: center;
}
.textarea{
    width: 300px;
    height: 50px;
    display: block;
    margin: 0 auto;
    border: 1px solid black;
    text-align: right;
    font-size: 41px;
}
.calc__buttons-wrap{
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    margin: 0 auto;
}
.calc__btn{
    width: 50px;
    height: 50px;
    margin: 10px;
}
.calc__btn_smooth{
    grid-column-start: 4;
    grid-column-end: 5;
    grid-row-start: 3;
    grid-row-end: 5;
    height: 120px;
}
.calc__btn_double-zero{
    grid-column-start: -4;
    grid-column-end: -2;
    width: 130px;
}