body {
  background-color: lightblue;
}

td {
  text-align: center;
  width: 100px;
}

.header {
  text-decoration: underline;
}

.old-activity {
  color: green;
}

.latest-activity {
  color: yellow;
}

.current-activity {
  color: red;
}

.next-activity {
  color: black;
  font-weight: 500;
}

.hidden {
  opacity: 0;
}

.visible {
  opacity: 1;
}