app.css

body {
  width: 100%;
  margin: 0;
  padding: 1rem;
}
ul {
  display: block;
  margin: 0 auto;
  padding: 0;
}
li {
  clear: both;
  width: 100%;
  margin-bottom: 1rem;
}
li input {
  font-size: 0.8rem;
}
[name="title"] {
  width: 60%;
  margin-right: 1rem;
}
.category {
  display: block;
  width: 60%;
  font-size: 0.9rem;
}
input[type="checkbox"]:checked + [name="title"] {
  text-decoration: line-through;
}
.completed {
  display: none;
  width: calc(40% - 3rem);
  padding-left: 1rem;
}
input[type="checkbox"]:checked + [name="title"] + .completed {
  display: inline-block;
}
[name="title"] {
  float: left;
}
[name="date"] {
  display: block;
  width: 100%;
}
#logout {
  float: right;
}
#auth {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 96%;
  max-width: 400px;
  text-align: center;
  -webkit-transform: translate(-50%, -50%);
  -moz-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}
#auth input,
#auth button {
  display: block;
  margin: 0 auto 1rem;
}
h2 {
  margin-top: 3rem;
  font-size: 1.25em;
}
h3 {
  font-size: 0.75em;
}
.heading {
  padding-bottom: 0.5rem;
  border-bottom: 0.1rem solid #333;
}
#user, #total {
  float: left;
}
main {
  clear: both;
}