.p-anima-3 {
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.1);
  overflow: hidden;
  position: relative;
  transition: color 0.4s;
}
.p-anima-3:hover {
  color: #333;
}
.p-anima-3::before {
  content: "";
  display: block;
  background-color: #fff;
  position: absolute;
  top: 0;
  left: 0;
  width: 120%;
  height: 100%;
  transform-origin: right top;
  transform: skewX(-30deg) scaleX(0);
  transition: transform 0.4s;
}
.p-anima-3:hover::before {
  transform-origin: left top;
  transform: skewX(-30deg) scaleX(1);
}

.p-anima-3 span {
  position: relative;
  z-index: 1;
}

/* アニメーションとは関係のないスタイル（ボタンの見た目など） */
body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}
.c-btn {
  display: block;
  color: #fff;
  font-size: 20px;
  font-weight: bold;
  text-align: center;
  background-color: #333;
  border-radius: 3px;
  width: 300px;
  margin: auto;
  padding: 20px 0;
  text-decoration: none;
}