Leaflet.help.css

.leaflet-control-help .leaflet-control-help-button {
  font-weight: 700;
  font-size: 1.5em;
}

.help-panel {
  z-index: 10;
  position: absolute;
  left: 50%;
  top: 50%;
  max-width: 80%;
  max-height: 80%;
  overflow: auto;
  -webkit-transform: translate(-50%, -50%);
  -moz-transform: translate(-50%, -50%);
  -ms-transform: translate(-50%, -50%);
  -o-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
  padding: 1em 2em 1em 1em;
  border-radius: 4px;
  background: white;
  background: rgba(255, 255, 255, 0.9);
  box-shadow: 0 0 10px rgba(128, 128, 128, 0.5);
  opacity: 1;
  transition: all 0.1s;
  transition-timing-function: ease-out;
}
.help-panel.pending {
  top: calc(50% + 5px);
  opacity: 0;
}
.help-panel.dismissed {
  opacity: 0;
  transition: opacity 0.15s;
}
.help-panel p.title {
  font-size: 1.4em;
  font-weight: 700;
  margin: 0;
}
.help-panel h1 {
  font-size: 1.2em;
}
.help-panel h2 {
  font-size: 1.1em;
}
.help-panel h3 {
  font-size: 1.0em;
}
.help-panel a.close {
  position: absolute;
  top: 0px;
  right: 0px;
  padding: 0.25em 0.5em 0 0;
  text-decoration: none;
  color: #ccc;
  font-size: 1.5em;
}