My guess is that it could be from the Plantation like the "Inner Wall" on CS3D seeing that there's a small block you can hide behind and also seeing the challenge start with 41 HP and having the spur and booster v2.0 already but that's just a guess anyway
I've playing the hell several times to get this 2 "Secret" themes, my question is, what is the time or how unlock these themes, because i beat the hell in "4'27'9" and nothing happend