.spoiler, .spoiler a {
  color: black;
  background-color: black;
}

.spoiler:hover, .spoiler:hover a {
  color: gray;
}

/* https://flaviocopes.com/css-system-fonts */
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto",
  "Oxygen", "Ubuntu", "Helvetica Neue", Arial, sans-serif, "Apple Color Emoji",
  "Segoe UI Emoji", "Segoe UI Symbol";
}

/* https://stackoverflow.com/a/40032327 */
pre {
  white-space: pre-wrap;
  word-wrap: break-word;
  text-align: justify;
}