New stairs placement doesn't seem to work correctly on Android

[Oblomov]

I'm still investigating the issue, but it seems that the new stairs placement logic results in stairs being placed upside-down on Android, even though it seems to work correctly on the desktop.

[Oblomov]

After some more testing, I think the peculiarity on Android comes, I think, from the fact that you can place a node on a different part of the screen compared to the central node which, on desktop, corresponds to the one you're actually pointing at.

[Oblomov]

I suspect that #166 might fix this as well, but I still need to check.