body {
  font-family: "Arial", sans-serif;
  color: #FFFFFF;
  background-color: #000000;
  margin: 0;
  padding-bottom: 20px;
  min-height: 100vh;
  position: relative;
}

input {
  width: 100px;
  margin-bottom: 10px;
}

button {
  background-color: blue;
  color: white;
  padding: 10px;
  cursor: pointer;
}

.disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

p {
  display: none;
}

#username:invalid + p {
  display: block;
}

.footer-text {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  font-size: 0.6em;
  color: #FFFFFF;
  background-color: #000000;
  padding: 5px 0;
  z-index: 1000;
}