yeah i forget battle circuit!, but i also dont remenber right now the year (i think that avp is from 94 and battle circuit from 95 not?).
i dont remenber it well since i see all capcom games in arcades, with only that exception.
the secret level:
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and YES finally i discover that secret level. is in the stage 2 (really stage 1 hospital if you not count that cool "house stage 0" that bonusjz made).
well for access to that secret level, you must wait in front of the elevator. that means kill all the enemys around there, but not continue your way to the right!.
then keep near the elevator and finally you can play that secret stage.
thanks to the guy that talk about this in one of the previous post.
that level are the library and the secret laboratory. saddly my game crash since i make some experiments by try to add 4 players and look what happens with that...
i let the other 3 players die before entering the elevator, passed the library stage, and in the follow level (the secret laboratory) against the doctor boss, just in the moment after the doctor transformation, the game do a crash and exits the openbor.
sure this must be for the lack of memory for support 4 players when the game is maked for 2 pls only with lots of enemies and features, and even if the other 3 players dies, the memory usage of the engine remenber that thing (the 4 players), and are overpassed (well, thats i suppose).
but also maybe can be some of those damn-rare random game crashes that else game can have, who knows... ¿?
i only have that fail 1 time by now. so i dont know if that crash happens always or not.
but i supposed that yes, and it must happens always with use 4 players there.
anyway is only one experiment i make. one experiment that indeed crash with irony in the laboratory level. (experiment-laboratory)

by the way, is a pity that the game dont have 3 players like the original mame arcade game, and not only 2. (or even 4 thinking in that nsx version2)
but this game is very cool, and maybe due to that it uses all the memory of the engine by now.
anyway, maybe the game can have more memory if not keep in the ground the death corpses of all the enemies... a cool detail, but that sure use memory.
ps: about the thing i explain yesterday about cadillacs and avp... well really this nsx vers1 have more moves that cadillacs and dinosaurs. but sure it have less that these unreleased cool nsx version 2...
ps2: can be a great idea if someone make a gift or something with that secret level cheat and all the moves for the 3 chars.
in that way really the game can be enjoyed much more...