body {
  font-family: sans-serif;
}

#todo-list {
  width: 300px;
  margin: 0 auto;
}

input {
  width: 100%;
  padding: 10px;
  border: 1px solid #ccc;
}

button {
  background-color: #000;
  color: #fff;
  padding: 10px;
  border: none;
  cursor: pointer;
}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
}

li {
  border-bottom: 1px solid #ccc;
}

.completed {
  text-decoration: line-through;
}