body {
    font-family: 'Arial', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f0f0f0;
  }
  #container {
    position: relative;
    width: 80%;
    height: 80%;
    border: 2px dashed #aaa;
    background-color: #fff;
    overflow: hidden;
  }
  .package {
    position: absolute;
    width: 50px;
    height: 50px;
    background-image: url("assets/red_package.png");
    background-size: contain;
    cursor: move;
    z-index: 100;
  }
  .house {
    position: absolute;
    width: 80px;
    height: 80px;
    background-image: url("assets/house.png");
    background-repeat: no-repeat;
    background-size: contain;
    border-radius: 5px;
    z-index: 50;
  }
  .btn {
    margin-top: 20px;
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
  }
  #flexbox {
      width: 100%;
      height: 100%;
  }
  .sticky-header {
      background-color: #333;
      color: #fff;
      position: fixed;
      width: 100%;
      top: 0;
      z-index: 1000;
      left: 0;
  }