calculator.css

.calculator {
  width: 234px;
  height: 322px;
  box-shadow: 0 20px 40px 0 rgba(0,0,0,0.5);
  border-radius: 5px;
  margin: 50px auto;
  border: 1px solid #656565;
  overflow: hidden;
  box-sizing: border-box;
  -webkit-user-select: none;
}

.calculator__screen {
  position: relative;
  background-color: rgba(0,0,0,0.4);
  width: 234px;
  height: 79px;
  box-sizing: border-box;
  font-family: -apple-system, "San Francisco";
  font-weight: 100;
  color: #FFF;
  letter-spacing: 0.3px;
  padding: 24px 13px 0;
  text-align: right;
  backdrop-filter: blur(5px);
}

.calculator__display {
  position: absolute;
  bottom: 0;
  right: 13px;
  font-size: 46px;
  white-space: nowrap;
}

.calculator__key-row {
  display: flex;
  flex-direction: row;
  justify-content: flex-start;
  flex-wrap: wrap;
}

.calculator__key {
  display: inline-block;
  width: 58px;
  height: 48px;
  color: #000;
  border-top: 1px solid #8E8E8E;
  border-right: 1px solid #8E8E8E;
  font-family: -apple-system, "San Francisco";
  text-align: center;
  line-height: 48px;
  font-size: 21px;
  font-weight: 400;
  box-sizing: border-box;
}

.calculator__key-row:last-child .calculator__key {
  height: 49px;
}

.calculator__key_command {
  background: #D6D6D6;
  font-size: 18px;
}

.calculator__key_command[data-command='plus-minus'] {
  background-image: url(plus-minus.svg);
  background-position: 50% 50%;
  background-repeat: no-repeat;
  background-size: 21px 14px;
}

.calculator__key_digit {
  background: #E0E0E0;
}

.calculator__key_operator {
  color: #FFF;
  background: #F79231;
  border-right: none;
  font-size: 32px;
  font-weight: 200;
  line-height: 38px;
}

.calculator__key_wide {
  width: 116px;
  text-align: left;
}

.calculator__key_wide:before {
  content: '';
  display: inline-block;
  width: 23px;
}

.calculator__key_selected {
  box-shadow: inset 1px 1px 0 0 #8E8E8E, inset -1px -1px 0 0 #8E8E8E;
}

.calculator__key_pressed.calculator__key_operator {
  color: #4C666E;
  background-color: #C37431;
}

.calculator__key_pressed.calculator__key_digit {
  background-color: #B2B2B2;
}

.calculator__key_pressed.calculator__key_command {
  background-color: #A9A9A9;
}