html, body {
  height: 100%;
  width: 100%;
  overflow: hidden;
  margin: 0;
  font-family: Arial;
  color: white;
}

.bg_red {
  background: #3F0000;
  background: radial-gradient(square, #8E0000 0%, #3F0000 100%);
}

.bg_black {
  background: #000000;
  background: radial-gradient(circle, #282828 0%, #000000 100%);
}

a:link, a:hover, a:visited, a:active {
  color: white;
  text-decoration: none;
}

.loading {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.experiment-url {
  position: absolute;
  bottom: 10px;
  right: 10px;
  padding: 8px;
  z-index: 1;
  font-size: 11px;
  background: black;
  letter-spacing: 0.5px;
  border: 1px solid white;
}

.theme_menu {
  position: absolute;
  bottom: 0;
  left: 0;
  padding: 5px;
  z-index: 1;
}

.theme_btn {
  position: relative;
  display: inline-block;
  width: 40px;
  height: 40px;
  text-align: center;
  border: 1px solid white;
  font-size: 14px;
  margin: 5px;
  cursor: pointer;
  font-weight: bold;
}

.theme_btn span {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}