Many rules can be made cumulative. For example, "If a 7 is played, the next player picks up two cards and forfeits his turn or plays another 7, if he plays another 7, the player after him picks up 4 cards and forfeits his turn or plays another 7, etc." Generally it is desirable to have the more complex rules on a rarer trigger so that the players are not overly taxed by any one rule. The very best rules are creative, playable and fun.