style.css

body, html {
    margin: 0;
    padding: 0;
    background-color: black;
}

* {
    font-family: sans-serif;
}

.fullscreen {
    width: 100vw;
    height: 100vh;
    overflow: hidden;
}

.fullscreen > * {
    width: 100%;
    height: 100%;
}

.overlay {
    position: fixed;
    width: 100%;
    height: 100%;
}
.overlay h2 {
    position: fixed;
    left: 50%;
    top: 80%;
    color: rgb(31, 179, 68);
    transform: translate(-50%, -50%);
    text-shadow: 0px 0px 5px rgb(0, 173, 52);
}
.overlay .show {
    display: inline-block;
}

.overlay .hide {
    display: none;
}

a.back {
    display: block;
    padding: 5px 10px;
    background: #fff;
    border: 1px solid #ccc;
    cursor: pointer;
    text-decoration: none;
    color: #000;
}

a.back:hover {
    background: #ddd;
}

#main-menu {
  top: 50%;
  left: 50%;
  right: 50%;
  bottom: 50%;
  position: absolute;
}

.main-menu .main-menu-contents {
  transform: translate(-50%, -50%);
  background-color: rgb(22, 22, 22);
  color: rgb(248, 110, 110);
  width: 20vw;
  height: 4vw;
  text-align: center;
  font-size: 3vw;
  margin: 4px 2px;
  opacity: 0.6;
  transition: 0.3s;
  cursor: pointer;
}

.main-menu-contents:hover {
  background-color: rgb(95, 0, 0);
}

.options-menu {
    display: none;
    top: 50%;
    left: 50%;
    right: 50%;
    bottom: 50%;
    position: absolute;
}

.options-menu .options-contents {
    display: none;
    transform: translate(-50%, -50%);
    background-color: rgb(22, 22, 22);
    color: rgb(248, 110, 110);
    width: 20vw;
    height: 4vw;
    text-align: center;
    font-size: 3vw;
    margin: 4px 2px;
    opacity: 0.6;
    transition: 0.3s;
    cursor: pointer;
}

.input-label {
    display: inline-block;
    text-align: right;
    font-size: 2vw;
    color: white;
}

.endingScene {
    display: none;
    text-align: center;
    top: 50%;
    left: 50%;
    right: 50%;
    bottom: 50%;
    color: gold;
}