Zombie-apocalypse

This is not my idea, this is idea of my little brother. His idea not very easy. 1 zombie from 5000 will with purple crystal in head. He can spawn only in night start. Better not kill he, otherwise will very many zombie. Before there wer 4-5 zombies in one crowd, but now, there will 50-70 zombie in one crowd. Zombies with armor and weapon will appear more often. But during zombie apocalypse zombie with crystal not can spawn. Zombie apocalypse continue until morning. So it's better hurry, because during zombie-apocalypse start spawn skeleton riders, but on zombie-horse. And at present you can tame zombie-horse how ordinary horse. Thanks my brother.