h1 {color: #0000ff}

#col_left {width: 30%; float: left; }

#col_right {width: 70%; float: right ;}


#calc button {
    width: 100px;
    height: 100px;
    font-size: 50px;
}

.button-red{
    background-color:maroon;
    color: white;
}

.btn-orange {
    background-color:rgb(244, 215, 158);
}

.img-thumbnail {
    width: 30%;
    margin: 1%;
    border-radius: 5px;
}

.square {
  height: 200px;
  width: 200px;
  background: rgb(240, 235, 142);
}