/* 按钮样式，包括背景、文本和过渡属性 */
.btn {
  position: absolute;
  top:55%;
  width: 250px;
  display: flex;
  justify-content: center;
  align-items: center;

  padding: 15px 20px;
  background-color: #f2f924;
  border-radius: 40px;

  text-decoration: none;
  text-transform: uppercase;
  font-size: 1.5em;
  font-weight: 600;
  letter-spacing: .1em;

  transition: transform .1s;
  overflow: hidden;
}
.btn span {
  position: relative;
  color: rgb(255, 255, 255);
  transition: color .5s;
}
/* 悬停时文本颜色变化 */
.btn:hover span {
  color: rgb(0, 0, 0);
}


/* 悬停时会扩展开的圆圈样式 */
.btn::before {
  content: "";
  position: absolute;
  top: var(--y);
  left: var(--x);
  transform: translate(-50%, -50%);
  background-color: var(--clr);
  width: 0;
  height: 0;
  border-radius: 50%;
  transition: 1s, left 0s, top 0s;
}
.btn:hover::before {
  width: 200px;
  height: 200px;
}