/* ── Portal Nav：TOPBAR 內的跨站切換 icon ── */

.portal-nav-btn {
  /* 固定貼在所屬 .top-nav 右側，隨 topbar 一起 sticky，不再獨立浮動 */
  position: absolute;
  top: 50%;
  right: 40px;
  transform: translateY(-50%);
  z-index: 10;
  /* 與右下角 LINE 浮動按鈕 (#spath-line-float，見 js/background.js) 同尺寸 */
  width: 58px;
  height: 58px;
  padding: 0;
  margin: 0;
  border: none;
  border-radius: 0;
  background: transparent;
  box-shadow: none;
  outline: none;
  appearance: none;
  -webkit-appearance: none;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: opacity .2s, filter .2s;
}

.portal-nav-btn:hover {
  filter: brightness(1.15);
}

.portal-nav-btn img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  pointer-events: none;
}

.portal-nav-btn.is-flying {
  pointer-events: none;
  opacity: 0;
}

/* ── 飛行分身 ── */
.portal-flyer {
  position: fixed;
  z-index: 10000;
  pointer-events: none;
  will-change: transform;
}

.portal-flyer-glow {
  position: absolute;
  inset: -60%;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(255, 206, 92, 0.95) 0%, rgba(255, 69, 0, 0.4) 45%, transparent 72%);
  opacity: 0;
  transform: scale(0.4);
}

.portal-flyer-img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.portal-flyer-img--from { opacity: 1; }
.portal-flyer-img--to { opacity: 0; }

.portal-flyer--active {
  animation: portal-fly 1.1s cubic-bezier(.65, 0, .35, 1) forwards;
}

.portal-flyer--active .portal-flyer-img--from {
  animation: portal-crossfade-out 1.1s ease forwards;
}

.portal-flyer--active .portal-flyer-img--to {
  animation: portal-crossfade-in 1.1s ease forwards;
}

.portal-flyer--active .portal-flyer-glow {
  animation: portal-glow 1.1s ease forwards;
}

@keyframes portal-fly {
  /* 旋轉角度需落在 360 的倍數才會維持正面，避免落地時上下顛倒 */
  0%   { transform: translate(0, 0) scale(1) rotate(0deg); }
  45%  { transform: translate(var(--fly-dx), var(--fly-dy)) scale(var(--fly-scale)) rotate(380deg); }
  55%  { transform: translate(var(--fly-dx), var(--fly-dy)) scale(var(--fly-scale)) rotate(700deg); }
  100% { transform: translate(0, 0) scale(1) rotate(1080deg); }
}

@keyframes portal-crossfade-out {
  0%, 42%  { opacity: 1; }
  50%, 100% { opacity: 0; }
}

@keyframes portal-crossfade-in {
  0%, 42%  { opacity: 0; }
  50%, 100% { opacity: 1; }
}

@keyframes portal-glow {
  0%, 100% { opacity: 0; transform: scale(0.4); }
  50%      { opacity: 1; transform: scale(1); }
}

@media (max-width: 1000px) {
  .portal-nav-btn {
    top: 8px;
    right: 10px;
    transform: none;
    width: 52px;
    height: 52px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .portal-flyer { display: none; }
}