How does the royal rumble work?

a royal rumble is a 30 man over the top rope elimination match. 2 superstars start in the ring and every minute and a half a new wrestler enters the ring you can only be eliminated only by being tossed out the ring by a legal superstar if a wrestler who's already been eliminated knocks a wrestler out of the ring the superstar knocked out is allowed back in the last superstar remaning in the ring wins a shot at either the WWE title or WORLD HEAVYWEIGHT title at WRESTLEMANIA