body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: #f5f5f5;
    font-family: Arial;
  }
  
  .container {
    background: white;
    padding: 30px;
    border-radius: 10px;
    width: 300px;
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
  }
  
  input {
    padding: 10px;
    width: 70%;
  }
  
  .done {
    text-decoration: line-through;
    color: gray;
  }
  
  button {
    padding: 10px;
    cursor: pointer;
  }
  
  li {
    margin-top: 10px;
    cursor: pointer;
  }