body {
  margin: 0;
  padding: 0;
  font-family: "Open Sans", sans-serif;
  background-color: #111;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.checkbox {
  position: fixed;
  top: 40px;
  right: 40px;
  -webkit-appearance: none;
  width: 80px;
  height: 40px;
  background-color: #ccc;
  border-radius: 20px;
  cursor: pointer;
  outline: none;
}

.checkbox:checked {
  background-color: #3498db;
}

.checkbox::before {
  content: "";
  position: absolute;
  width: 32px;
  height: 32px;
  background-color: #fff;
  border-radius: 20px;
  top: 4px;
  left: 4px;
  transition: .3s linear;
}

.checkbox:checked::before {
  left: 44px;
}

.page-content {
  width: 800px;
  background-color: #fff;
  padding: 50px;
  display: flex;
  filter:brightness(20%);
}

.page-content img {
  margin-right: 30px;
}

.page-content h1 {
  margin-top: 0;
  font-size: 26px;
  text-transform: uppercase;
}

.page-content {
  font-size: 18px;
  text-align: justify;
}

.checkbox:checked + .page-content {
  filter:brightness(100%);
}