.calculator{display:grid;grid-template-columns:repeat(4,1fr);grid-auto-rows:minmax(50px,1fr);font-size:30px;width:600px;margin:20px auto;line-height:50px}.calculator .display{grid-column:1/5;background-color:#444;color:#fff}.calculator .zero{grid-column:1/3}.calculator .btn{background-color:#eee}.calculator .operator{background-color:orange}.calculator .btn,.calculator .operator{cursor:pointer;border:1px solid #555}.calculator .equal{background-color:#ff4500;opacity:.8}.calculator .equal:hover{opacity:1}#app{font-family:Avenir,Helvetica,Arial,sans-serif;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;text-align:center;color:#2c3e50;margin-top:60px}