<button class="cp_button12">button</button>

.cp_button12 {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 160px;
  margin: 0.4em;
  padding: 1em;
  color: #ffffff;
  background: #29b6f6;
  border: 1px solid #29b6f6;
  border-radius: 0;
  box-shadow: 0 0 1px rgba(0, 0, 0, 0);
  cursor: pointer;
  transform: translateZ(0);
}
.cp_button12:before {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  content: '';
  border: rgba(41,182,246,0.5) solid 4px;
  transition-duration: 0.3s;
  transition-property: top right bottom left;
}
.cp_button12:hover:before {
  top: -8px;
  right: -8px;
  bottom: -8px;
  left: -8px;
  opacity: 1;
}
.cp_button12:active {
  color: #ffffff;
  background-color: #0288d1;
}
.cp_button12:active:before {
  top: -3px;
  right: -3px;
  bottom: -3px;
  left: -3px;
}
.cp_button12:focus:hover,
.cp_button12:focus,
.cp_button12:active:hover,
.cp_button12:hover {
  color: #ffffff;
  border: 1px solid #29b6f6;
}