最近，我想在容器中添加一个按钮，同时添加图标和文本。但按钮不能在中间对齐。我甚至不确定图标是否在中间对齐。我试着调整上边的%和左边的%但不动。

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.container {
  position: relative;
  width: 550px;
  height: 350px;
  background-color: rgba(255, 255, 255, 0.7);
  margin: 20px auto;
  border-radius: 15px;
  box-shadow: 0 0 20px 0px rgba(0, 0, 0, 0.6);
}

.container h1 {
  margin: 0;
  padding: 0;
  font-size: 30px;
  text-align: center;
  position: relative;
  top: 20%;
  transform: translateY(-80%);
}

.icon {
  width: 40%;
  height: 40%;
  margin: 0;
  left: 30%;
  top: 15%;
  transform: translateX(-70%, -80%);
  position: relative;
}

.button {
  background-color: rgba(231, 231, 231, 1);
  border: none;
  padding: 12px 25px;
  margin: 0;
  text-align: center;
  display: block;
  font-size: 16px;
  color: black;
  border-radius: 12px;
  position: relative;
  top: 50%;
  left: 50%;
}

<div class="container">
  <h1>Selamat Datang ke Kuiz FizikMudah!</h1>
  <img src="https://via.placeholder.com/500x400.png" class="icon">
  <a href="index.php"><button class ="button" type="button">Masuk</button></a>
</div>

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