html { font-size: 16px; }
body { font-size: 1rem; line-height: 1.6; margin: 16px; }

section {
  padding-bottom: 50px;
}

.mainContainer {
  position: relative;
  width: 100%;
  max-width: 640px;   /* 桌面上不會超過原本寬度 */
  margin: 0 auto;
  height: 0;
  padding-top: 56.25%;
}

.content, .adContainer {
  position: absolute;
  inset: 0;           /* 等同 top/right/bottom/left 全為 0 */
}

.contentElement {
  width: 100%;
  height: 100%;
  object-fit: cover;  /* 或用 contain 視需求 */
  overflow: hidden;
}

.button {
  display: inline-block;
  margin-top: 10px;
  vertical-align: top;
  width: 100%;
  max-width: 350px;
  height: 3rem;           /* 約 48px */
  padding: 0 0.75rem;
  font-size: 1rem;        /* 依使用者設定縮放 */
  color: white;
  text-align: center;
  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.25);
  background: #2c3e50;
  border: 0;
  border-bottom: 2px solid #22303f;
  cursor: pointer;
  -webkit-box-shadow: inset 0 -2px #22303f;
  box-shadow: inset 0 -2px #22303f;
}