The Four Tubes

[aquaMat]

@Toybox:

You are right. In the first (or first two) versions I accidentially ommitted the BBB for the green tube !
This has neem fixed in the meantime, although I'm not sure whether that update has already been released. (I'll check later).

@ arevn:

As I said before:  No matter in what order you travel through the tubes you will always be able to finish (= access the final section).
If you didn't in that one instance, I'm sure it had nothing to do with the

tube order

but was due to some other oversight of you (and I guess I know which).

The whole door/key color system is very logical, it works similar in every tube.