* {
  box-sizing: border-box;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: Helvetica, Arial, sans-serif;
  height: 100vh;
  margin: 0;
  background-image: url(bg.png);
  background-color: #ff9501;
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center center;
  background-attachment: fixed;
}

.calculator {
  width: 400px;
  margin-top: 100px;
}

.calculatorTitle {
  color: white;
  text-align: right;
}

.calculatorTitle h1 {
  margin: 0;
  padding: 25px;
  font-size: 100px;
  font-weight: 100;
  overflow-x: auto;
}

.calculatorBtn {
  display: grid;
  place-items: center;
  grid-template-columns: repeat(4, 1fr);
  width: 400px;
}

button {
  font-size: 35px;
  color: #ffffff;
  background-color: #333333;
  box-shadow: 0 0 0 1px #000000; 
  border-radius: 50%;
  border: 0;
  height: 80px;
  width: 80px;
  margin: 5px;
  
  &:focus {
    background-color: #737373;
    outline: 0;
  }
  
  &:nth-child(-n+3) {
    background-color: #a6a6a6;
    color: #000000;
    &:focus {
      background-color: #d9d9d9;
    }
  }
  
  &:last-child, 
  &:nth-child(4n-4) {  
    background-color: #ff9f0a;
    &:focus {
      background-color: #ffffff;
      color: #ff9f0a;
    }
  }
}

.zeroBtn {
  width: 90%;
  grid-column: 1 / span 2;
  -webkit-border-radius: 50px;
  -moz-border-radius: 50px;
  border-radius: 70px;
  text-align: left;
  padding-left: 35px;
}

button:hover {
  opacity: .8;
  cursor: pointer;
}




/* Mobile */
@media (max-width:768px) {
  body {
    background-image: none;
    background-color: rgb(0, 0, 0);
    overflow: hidden;
  }

  .calculatorBtn {
    width: 300px;
    margin-bottom:120px;
    margin-left: 5px;
  }

  .calculatorTitle h1 {
    font-size: 130px;
  }
}