as a hack of the original super mario bros., extra mario bros. is very technically impressive: a metroid-like labrynthine layout, power-ups that expand mario’s moveset, auto-scrolling sections, switches that change the layout of the play area, screen-filling bosses. if you’re adding so much new code, though, why not just make a new game? super mario bros. doesn’t need double jumps or giant laser bowsers; that’s why there aren’t any.
the conclusion i came to is, i think, the reason the hack is so interesting: by hacking these features into shigeru miyamoto and takashi tezuka’s seminal platformer, the author is grounding the tropes of contemporary platformer design in the framework of the game that popularized the platformer. essentially, this 2005 hack is super mario bros. informed by twenty years of designers riffing off of super mario bros.
the hack is also a little deceptive: it’s a hack of super mario bros., but it’s actually an homage to super metroid. that it manages to successfully replicate metroid’s maze structure in a game that only scrolls in one direction is particularly admirable: this is a harder task than it might seem, and entails ensuring that the player understands and is aware of her options and has plenty of avenues for returning to previous areas. after a little while of play you’ll come to recognize the two-way “antechambers” that serve the function of metroid’s elevator rooms. (note, too, how the author uses piranha plants to distinguish between pipes which are used to travel and pipes that are scenery or one-way doors.)