.btn {
  position: relative;
  overflow: hidden;
}

.btn::after {
  content: '';
  position: absolute;
  width: 0;
  height: 0;
  background: rgba(255,255,255,0.25);
  border-radius: 50%;
  transform: translate(-50%, -50%);
  pointer-events: none;
}

.btn:active::after {
  width: 200px;
  height: 200px;
  transition: width 0.4s ease, height 0.4s ease;
}

.fade-in {
  animation: fadeIn 0.4s ease forwards;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: none; }
}

/* Seal 动画 */
#seal-anim {
  position: fixed;
  inset: 0;
  background: #0f1115;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  z-index: 20;
}

#seal-anim .circle {
  width: 120px;
  height: 120px;
  border-radius: 50%;
  border: 2px solid rgba(255,255,255,0.2);
  animation: pulse 1.2s infinite;
}

#seal-anim .text {
  margin-top: 20px;
  opacity: 0.6;
  letter-spacing: 2px;
}

@keyframes pulse {
  0% { transform: scale(0.8); opacity: 0.4; }
  50% { transform: scale(1.1); opacity: 1; }
  100% { transform: scale(0.8); opacity: 0.4; }
}

/* 波纹 */
#water {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 9999;
}