body {
  font-family: Tahoma;
  margin: 0;
  background-color: grey;
}

#kontener {
  width: 30%;
  margin: 50px auto 50px auto;
  box-shadow: 10px 10px 5px rgba(0, 0, 0, 0.4);
}

@media only screen and (max-width: 720px) {
  #kontener {
    width: 80%;
  }
}

.kafel {
  display: block; /* Aby wyświetlały się jeden pod drugim. */
  padding: 20px;
  border: none;
  text-align: center;
  color: white; /* Kolor czcionki.*/
  font-size: 20px;
  cursor: pointer;
  text-decoration: none;
  outline: none;
}

.kafel:nth-child(1) {
  background-color: orange;
}
.kafel:nth-child(2) {
  background-color: red;
}
.kafel:nth-child(3) {
  background-color: brown;
}
.kafel:nth-child(4) {
  background-color: tan;
}
.kafel:nth-child(5) {
  background-color: magenta;
}
.kafel:nth-child(6) {
  background-color: violet;
  display: none;
}
.kafel:nth-child(7) {
  background-color: green;
}
.kafel:nth-child(8) {
  background-color: blue;
}
.kafel:nth-child(9) {
  background-color: black;
}

hr {
  width: 40%;
  height: 1px;
  border: none;
  background-color: white;
}

@media only screen and (max-width: 720px) {
  hr {
    width: 80%;
  }
}