Metroid and metroidvania
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When the first Metroid, metroidvania did not exist; and this is not atypical. It is very atypical, on the contrary, that they did not even exist in subsequent years: Super Mario Bros. had several predecessors, but its Big Bang was such that it inspired hundreds of titles, which in turn contained dozens of clones. For Metroid, partly due to lower sales - but that can't be the only reason - it didn't happen. Maybe that's because Metroid itself was already a mix between a 2D platformer and an exploratory game. The fact is that in the following years it did not trigger emulation phenomena: even Castlevania, also born in 1986, at the time had nothing to do with what it would become. It was beautiful, but straightforward.