Minecraft is a first-person fighter/sandbox construction game created by Mojang AB.
We are preparing for the weekly snapshot... so let's feature creep!
Up-side-down stairs are the same block as the normal stairs, but flipped when you place them on the bottom of another (from below)
Not doing up-side-down half-slabs right now, but maybe later. Next week will be bug-fixing week for a possible 1.2 release --Jeb_