button {
  margin: 0 20px 40px;
  padding: 1em 2em;
  border: none;
  box-sizing:border-box;
  width:300px;
  display: inline-block;
  font-size: 114%;
  position: relative;
  cursor: pointer;
}
button::before,
button::after {
   box-sizing:border-box;
}
@keyframes poyo2 {
    0% { transform: scale(1); }
   50% { transform: scale(.9); }
   60% { transform: scale(1.1); }
   70% { transform: scale(.95); }
   80% { transform: scale(1.05); }
   90% { transform: scale(.98); }
  100% { transform: scale(1); }
}

/*　buttonG　*/
.buttonG {
  border:3px solid rgba(147,162,0,1);
  background-color: transparent;
  color: rgba(147,162,0,1);
  transition: .6s all;
  position: relative;
}
.buttonG::before {
  display: block;
  width: 100%;
  height: 100%;
  background-color: rgba(147,162,0,1);
  position: absolute;
  left: 0;
  top: 0;
  transition: .3s all;
  transform-origin: 50% 50%;
  z-index:-1;
}
.buttonG::after {
  display: block;
  width: 100%;
  height: 100%;
  background-color: #FFF;
  position: absolute;
  left: 0;
  top: 0;
  transition: .3s all;
  transform: scale(1,0);
  transform-origin: 0 50%;
  opacity: 0;
  z-index:-1;
}
.buttonG:hover {
  color: rgba(147,162,0,1);
}
.buttonG:hover::after {
  transform: scale(1,1);
  opacity: 1;
}