This is probably a really stupid question, but as someone who is just now sort of getting into pokemon competitively, I was wondering something about dual types and effectiveness/immunity. Say you have a steel/fairy type. I know it is immune to poison even though the fairy type would normally take double damage. Why is this from a game design perspective? Why not make it take normal damage to reflect only a partial immunity from steel lessened by the fairy typing? Would this just overcomplicate things? Thanks