.tip-btn{
  margin-left: 4px;
  padding: 0;
  background: none;
  border: none;
  cursor: pointer;
  font: inherit;
  line-height: 1;
  vertical-align: middle;
}

/* 実体tooltip（JSでbody直下に1個だけ作る） */
.oai-tooltip{
  position: fixed;              /* viewport基準で確実に収める */
  z-index: 9999;
  max-width: min(280px, calc(100vw - 24px)); /* 画面幅に合わせて縮む */
  padding: 10px 12px;

  background: #333;
  color: #fff;
  font-size: 12px;
  line-height: 1.6;
  border-radius: 8px;
  box-shadow: 0 6px 18px rgba(0,0,0,.25);

  opacity: 0;
  transform: translateY(4px);
  pointer-events: none;
  transition: opacity .12s ease, transform .12s ease;
}

.oai-tooltip.is-show{
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

/* 矢印（任意） */
.oai-tooltip::before{
  content: "";
  position: absolute;
  width: 0; height: 0;
  border-left: 7px solid transparent;
  border-right: 7px solid transparent;
  border-bottom: 7px solid #333;
  top: -7px;
  left: var(--arrow-left, 16px);
}