* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  display: flex;
}

.calculadora {
  width: 100vw;
  height: 100vh;
  display: grid;
  grid-template-rows: 1fr 3fr;
}

.pantalla {
  background: #333;
  padding: 6%;
  padding-top: 15%;
  text-align: right;
  overflow: hidden;
}

.pantalla--primaria {
  font-size: 2.5rem;
  color: #fff;
  overflow-x: auto;
}

.pantalla--secundaria {
  font-size: 1.7rem;
  color: #777;
  display: flex;
  justify-content: flex-end;
  align-items: center;
}

.teclado {
  display: flex;
  background: #111;
}

.boton {
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  cursor: pointer;
}

.boton:active {
  animation: animarSombra 0.5s;
}

@keyframes animarSombra {
  0%   { background: black; }
  50%  { background: skyblue; }
  100% { background: #333; }
}

.isquierdo {
  width: 78%;
  display: grid;
  grid-template-rows: repeat(4, 1fr);
  grid-template-columns: repeat(3, 1fr);
}

.derecho {
  width: 22%;
  display: flex;
  flex-direction: column;
  justify-content: space-around;
  border-left: 2px solid #333;
  border-right: 5px solid #9af;
}

.derecho .boton {
  color: #2299ee;
  font-weight: bold;
  font-size: 1.6rem;
}