align-items and justify-content with search bar

Im trying to make a simple search bar in html and css. However, justify-content and align-items arent working. Could someone help me figure out why?

https://codepen.io/Lavender786/pen/yLYwRBP

input[type=text] {
  width: 400px;
  box-sizing: border-box;
  border: 2px solid #ccc;
  border-radius: 4px;
  font-size: 16px;
  background-color: white;
  background-position: 10px 10px; 
  background-repeat: no-repeat;
  padding: 12px 20px 12px 40px;
}

.container {
  align-items: center; 
  justify-content: center;
}

<div id = "container">
<form>
  <input type="text" name="search" placeholder="Search...">
</form>
</div>