The ledge Xianu is standing on is two-way and I'd like to find a clever way to use them, but I'm pondering over effective ways to demonstrate and explain them to the players. People less familiar with KS+ may not know of the existence of drop-down ledges, let alone how to work them. I'll probably have to break the fourth wall with ingame text to explain it; I'd rather not but needs must. So maybe it's a case of finding the least intrusive way of doing that.
This is something I struggled with as well when working on the prototype for
Deep Freeze. One-way is much easier to manage because players will often "accidentally" go through from below without even realizing. You even took advantage of this in
I Chased the Moon - I distinctly remember just automatically climbing up that one ledge, and it took me a few seconds to realize that you'd used a one-way object, there.
Ultimately, I think the best way to handle two-way would be a simple, visual explanation using a CO - something like this:
(Floor shifts kept visible for clarity.)
The first time the player walks over the two-way tile, a simple CO is spawned by a floor trigger, depicting a down arrow and an "s". This is the simplest way I could think of to depict depressing one key, holding it, and then pressing the other. When the player completes the action, they hit another floor trigger just below, and the CO disappears, indicating to the player that they've completed the action (though you could also have the second floor trigger spawn a little checkmark CO and make a nice sound, if that's the kind of atmosphere you're going for). You could even make it so that there's also a floor shift where the second floor trigger is that gives the player a flag so they'll never see the CO again, if you wanted. If you felt the need to show the player that they can also jump UP through these tiles (though I think that they'll be able to get that naturally, as is the case with one-ways), then you could easily place another two-way that they're forced to jump up through. From there, all you need to do is keep your tileset direction consistent enough so a player can tell whenever something is two-way, but I imagine you'll be able to handle that well enough.
All that said, my level has the benefit of having a similar graphic earlier, with only the down arrow, so the meaning of this one is something that should already be partially understood by the player. It also benefits from its simple visual presentation - this graphic won't clash with it. It may be a little tougher to create a similar graphic that fits for your level (may need smoother animation, shading, etc.), but I have faith that you can figure that out. I don't think a "voiced" explanation is too bad, but I feel that the simplicity of the CO allows the player to feel that, even though they've basically been told the inputs, there's still an itty-bitty sliver of figuring out the mechanic for themselves, and it does it with less word stuff, which I think is always better when you want to teach these kinds of things. There is
one major issue with this, which is ironically also only made possible by KS+, and it's that some players may actually not have their jump button bound to the "s" key. Then you're left hoping that they remember that jump is "s" - although I guess you could squeeze the word "jump" in there....
I already had a lot of respect for you simply 'cause you've made so many polished, complete decent-length levels, but seeing that this sort of level design subtlety is something you take into account bumps that even higher. Keep it up! And sorry for the huge amount of text for something so simple.