body {
  font-family: Verdana, sans-serif;
}

a:link, a:visited {
  background-color: white;
  color: black;
  border: 2px solid black;
  padding: 10px 20px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  border-radius: 4px;
}

a:hover, a:active {
  background-color: #778899;
  color: white;
  transition: background-color 0.5s;
}

#main-div{
    display: flex;
    width: 50%;
}

.sloupec{
    flex: 50%;
    padding: 10px;
}