.flash {
  min-width: 200px;
  max-width: 94vw;
  position: fixed;
  top: 1rem;
  left: 50%;
  padding: 1rem 1.5rem;
  border-radius: 0.5rem;
  transform: translateX(-50%);
  background: #333;
  color: white;
  overflow: hidden;
  box-shadow: 0 4px 10px rgba(0,0,0,0.2);
  transition: opacity 0.3s;
  animation: flash-hide 3s forwards;
}
.flash-button {
  border: none;
  top: 50%;
  right: 0.5rem;
  position: absolute;
  background: none;
  color: #aaa;
  font-size: 1.25rem;
  transform: translateY(-50%);
  line-height: 1;
  cursor: pointer;
}
.flash-bar {
  width: 100%;
  height: 4px;
  position: absolute;
  bottom: 0;
  left: 0;
  background: #525252;
  transform-origin: left;
  transform: scaleX(1);
  animation: flash-bar 3s linear forwards;
}
.flash.notice .flash-bar {
  background: #4ade80;
}
.flash.alert .flash-bar {
  background: #f34f4f;
}

/* 3秒で透明になるアニメーション */
@keyframes flash-hide {
  0% { opacity: 1; }
  90% { opacity: 1; }
  100% { opacity: 0; }
}

/* 3秒でバーが左→右に縮む */
@keyframes flash-bar {
  from { transform: scaleX(1); }
  to { transform: scaleX(0); }
}