/* =========================================================
   ページトップへ戻るボタン
   表示切り替えは js（.is-shown）
   ========================================================= */
.to-top {
  position: fixed;
  right: 24px;
  bottom: 24px;
  z-index: 80;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--main);
  display: grid;
  place-items: center;
  box-shadow: 0 3px 8px rgba(0, 0, 0, .25);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity .3s, visibility .3s, transform .3s;
}
.to-top.is-shown { opacity: 1; visibility: visible; transform: none; }
.to-top img { width: 22px; height: 22px; transform: rotate(-90deg); }

/* ---- Responsive ---- */
@media (max-width: 560px) {
  .to-top { right: 14px; bottom: 14px; width: 42px; height: 42px; }
}