body {
  font-family: 'Fira Mono', monospace;
}

#main {
  font-size: 28pt;
  margin: 3ex auto;
  width: 100%;
  text-align: center;
}

#settings {
  width: 100%;
  position: fixed;
  left: 0;
  bottom: 0;
  opacity: 0;
  transition: 0.8s;
}

#settings:hover {
  opacity: 1;
  transition: 0.8s;
}

#font_size {
  -webkit-appearance: none;
  width: 40%;
  height: 15px;
  border-radius: 5px;
  background: #e1eaef;
  outline: none;
}

#font_size::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 25px;
  height: 25px;
  border-radius: 50%;
  background: #40a7e3;
  cursor: pointer;
}

#font_size::-moz-range-thumb {
  width: 25px;
  height: 25px;
  border-radius: 50%;
  background: #40a7e3;
  cursor: pointer;
}

#options {
  margin: 3ex 40%;
  width: 40%;
}

.option {
  width: 180px;
  display: block;
  position: relative;
  padding-left: 26px;
  margin-bottom: 6px;
  cursor: pointer;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

.option input {
  position: absolute;
  opacity: 0;
  cursor: pointer;
  height: 0;
  width: 0;
}

.checkmark {
  position: absolute;
  top: 0;
  left: 0;
  height: 20px;
  width: 20px;
  border-radius: 5px;
  background-color: #e1eaef;
}

.option input:checked ~ .checkmark {
  background-color: #40a7e3;
}

.checkmark::after {
  content: "";
  position: absolute;
  display: none;
}

.option input:checked ~ .checkmark::after {
  display: block;
}

.option .checkmark::after {
  left: 6px;
  top: 2px;
  width: 5px;
  height: 10px;
  border: solid white;
  border-width: 0 3px 3px 0;
  -webkit-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  transform: rotate(45deg);
}