Fluxx games are highly confusing when you first encounter them. Why? Because you don't know what you need to do to win. All the victory conditions are dictated by the cards that the players lay down. What's more those victory conditions are constantly changing - or in a state of flux (hence the name). In truth they are not very hard to grasp at all - but there it is necessary to read a text on the cards in order to play. My 9 year old plays without issue.
Zombie Fluxx is one of the more enjoyable versions of the game. It was the first to introduce Creepers (negative effect) cards.
It's quick and easy - and can play out in anything from 2 to 30 mins for a two player game.