body, html {
  width: 100vw;
  height: 100vh;
}

.bggreen { background-color: green; }
.bggrey { background-color: grey; }
.bgred { background-color: red; }

.contents {
  overflow-x: hidden;
  overflow-y: auto;
}

.fblue { color: royalblue; }
.fgreen { color: green; }
.forange { color: orange; }
.fred { color: red; }
.hidden { display: none; }
.link { cursor: pointer; }