/* ヘッダー固定 */
.site-header {
  /* position: fixed;
  top: 0;
  left: 0;
  */
  width: 100%;
  background-color: #ffffff;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
  z-index: 999;
}

/*
.header-inner {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background-color: #ffffff;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
  z-index: 999;
  margin: 0 auto;
  padding: 10px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
*/

.scroll-underline {
  position: relative;
  display: inline-block;
  color: #222;
  text-decoration: none;
  font-weight: bold;
}

/* 初期状態：下線幅0 */
.scroll-underline::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 50%;
  transform: translateX(-50%);
  width: 0;
  height: 3px;
  background-color: #ff0000;
  transition: width 0.5s ease;
}

/* アクティブ時に下線が出現 */
.scroll-underline.visible::after {
  width: 100%;
}