.card {
    position: relative;
    width: 90%;               /* 基于容器宽度的 90% */
    max-width: 500px;         /* 最大 500px */
    aspect-ratio: 500 / 150;  /* 保持 500×150 比例 */
    padding: 2.5rem 1.5rem 1.5rem;
    border-radius: 1rem;
    text-align: center;
    transition: transform .3s, box-shadow .3s;
    cursor: pointer;
    text-decoration: none;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    background: #eee;         /* 默认背景，可被具体类覆盖 */
  }
  .card:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
  }

  .icon-top {
    position: absolute;
    top: -46px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    justify-content: center;
  }

  .card h3 { margin-top: 0; }
  .card p  { margin-top: .25rem; }

  .card-android { background: #ED8151; }
  .card-stk     { background: #445BB8; }
  .card-stk h3,
  .card-stk p { color: #FFF; }
  .card-iphone  { background: #DC817E; }

  @media (max-width: 768px) {
    .card h3 { font-size: 1rem; }
    .card p  { font-size: .875rem; }
  }