pikachu.css

.btn {
  background-color: #fad71e;
  padding: 10px 40px 12px;
  border-radius: 0 0 20px 20px;
  font-size: 16px;
  text-transform: uppercase;
  font-family: Open Sans, sans-serif;
  font-weight: 700;
  letter-spacing: 0.1em;
  position: relative;
  border: 2px solid #000;
  margin: 10px;
  display: inline-block;
  transition: box-shadow 1s linear;
  cursor: pointer;
  box-shadow:
    inset 0 -6px 0px #e19721;
}

.btn:hover {
  box-shadow:inset 0 -4px 0px #e19721;
}

.btn:hover:before {
  left: 8%;
}

.btn:hover:after {
  right: 8%;
}

.btn:before {
  transition: left 0.1s linear;
  left: 10%;
  top: calc(50% - 6px);  
}

.btn:after {
  transition: right 0.1s linear;
  right: 10%;
  top: calc(50% - 6px);  
}

.btn:before, .btn:after {
  content: '';
  background-color: #f82a13;
  width: 10px;
  height: 10px;
  border: 1px solid #000;
  border-radius: 50%;
  position: absolute;
}