:root {
  --jumbotron-padding-y: 3rem;
}

.jumbotron {
  padding-top: var(--jumbotron-padding-y);
  padding-bottom: var(--jumbotron-padding-y);
  margin-bottom: 0;
  background-color: #fff;
}
@media (min-width: 768px) {
  .jumbotron {
    padding-top: calc(var(--jumbotron-padding-y) * 2);
    padding-bottom: calc(var(--jumbotron-padding-y) * 2);
  }
}

.jumbotron p:last-child {
  margin-bottom: 0;
}

.jumbotron-heading {
  font-weight: 300;
}

.jumbotron .container {
  max-width: 40rem;
}

footer {
  padding-top: 3rem;
  padding-bottom: 3rem;
}

footer p {
  margin-bottom: .25rem;
}

.box-shadow { box-shadow: 0 .25rem .75rem rgba(0, 0, 0, .05); }

img:active {
  animation: shake 0.5s;
  animation-iteration-count: 1;
}

@keyframes shake {
  0% { transform: translate(1px, 1px) rotate(0deg); }
  10% { transform: translate(-1px, -2px) rotate(-1deg); }
  20% { transform: translate(-3px, 0px) rotate(1deg); }
  30% { transform: translate(3px, 2px) rotate(0deg); }
  40% { transform: translate(1px, -1px) rotate(1deg); }
  50% { transform: translate(-1px, 2px) rotate(-1deg); }
  60% { transform: translate(-3px, 1px) rotate(0deg); }
  70% { transform: translate(3px, 1px) rotate(-1deg); }
  80% { transform: translate(-1px, -1px) rotate(1deg); }
  90% { transform: translate(1px, 2px) rotate(0deg); }
  100% { transform: translate(1px, -2px) rotate(-1deg); }
}