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>tiny brain
Luxray is a sphinx.
>small brain
Luxray should be a Dark Type.
>mid brain
Luxray is a lion.
>big brain
Luxray is not a lion, Luxray is a lynx.
>galaxy brain
Luxray is an abstract feline creature. In terms of lore and primary inspiration it is 100% a mythological lynx, which were thought to possess the ability to see through solid walls akin to a modern electric X-ray machine. However, Luxray's physical design almost has nothing to do with lynxes at all besides being feline. Luxray is instead its own unique fictional big cat species, not trying to be any one thing, and pulls most of its physical design cues from lions and tigers. The former is alluded to by Luxray possessing a mane, which is longer in males, and furthermore by having the Rivalry ability. And the latter is represented by the stripes upon its forearms, and Luxray's Japanese name involving the word tiger.
Lastly, Luxray should NOT be a Dark Type due to its distinct lack of any villainous qualities, but it very clearly fits the aethetic perfectly and learns several Dark Type moves. And Luxray so far isn't known to be just or noble, either. So a single Pokédex entry revealing that Luxray acts cruel or is wily in some manner, is all it would take to justify having the Type. But without this, it should stay mono Electric.