<header>
  <h2 class="title">element.style.backgroundPosition</h2>
  <p class="description">Визначає позицію фону елемента.</p>
</header>
<main>
  <div class="result">
    <div class="demo-box" id="demoBox"></div>
    <div class="controls">
      <button onclick="changePosition('left top')">Лівий верх</button>
      <button onclick="changePosition('center center')">Центр</button>
      <button onclick="changePosition('right bottom')">Правий низ</button>
    </div>
  </div>
</main>

body {
  font-size: 16px;
  line-height: 1.5;
  font-family: monospace;
}

header {
  background-color: #f1f1f1;
  margin-bottom: 25px;
  padding: 15px;
  -webkit-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  -moz-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
}

header h2.title {
  padding-bottom: 15px;
  border-bottom: 1px solid #999;
}

header p.description {
  font-style: italic;
  color: #222;
}

.result {
  background-color: #f8f8f8;
  padding: 15px;
  -webkit-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  -moz-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  text-align: center;
}

.demo-box {
  width: 300px;
  height: 200px;
  margin: 0 auto;
  background-image: url('https://via.placeholder.com/300');
  background-size: cover;
  background-repeat: no-repeat;
  transition: background-position 0.5s;
}

.controls {
  margin-top: 20px;
}

.controls button {
  margin: 5px;
  padding: 10px;
  font-size: 14px;
  cursor: pointer;
}