style.css

body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f2f2f2;
  }
  
  .container {
    max-width: 600px;
    margin: 50px auto;
    padding: 20px;
    background-color: #fff;
    border-radius: 5px;
    box-shadow: 0px 0px 10px 0px rgba(0,0,0,0.1);
  }
  
  h1 {
    text-align: center;
  }
  
  input[type="text"] {
    width: calc(100% - 80px);
    padding: 10px;
    margin-bottom: 10px;
    border: 1px solid #ccc;
    border-radius: 3px;
  }
  
  button {
    padding: 10px 20px;
    background-color: #4CAF50;
    color: white;
    border: none;
    border-radius: 3px;
    cursor: pointer;
  }
  
  button:hover {
    background-color: #45a049;
  }
  
  ul {
    list-style-type: none;
    padding: 0;
  }
  
  li {
    padding: 10px;
    margin-bottom: 5px;
    background-color: #f9f9f9;
    border-radius: 3px;
  }
  
  .completed {
    text-decoration: line-through;
    color: #999;
  }