I know that this game becomes harder on the second playthrough (just like a lot of other NES games, like Super Mario Bros, Contra, Castlevania etc), but how many times does it keep doing this?
I played through this game a while ago and I noticed a few interesting although fairly simple things on the second playthrough, like enemies being faster and shooting more projectiles etc.
These kinds of things could in theory keep ramping up forever until the game could no longer handle it, so when exactly does it stop?