This bug isn't 100% reproducible, but it comes up more often than not for me.
When a cube is constructed and made hollow (50-70% for me, with a horizontal hole in it, IE, a windowframe; I haven't tested others), then textures can be applied to it normally, but the number of repeats per meter cannot. Clicking the 'apply' button causes the number to revert to what it was with no change to the object.
I have found that, as a workaround, I can make the cube solid, then alter the number of repeats per meter, then increment the hollow part again.
Even that is pretty buggy -- for instance, if I have a cube with five faces with the default texture, and one face (one of the faces with the hole in it, for the record) with an alternate texture, then it will return to the default texture when I increment the hollowness to 5%. However, incrementing beyond that -- 10% and up -- will return the alternate texture to where it belongs, and the inside face of the hollow part will take on the texture of that single, non-default-texture face.
Also, I've been having occasions when I click on the ground to create an object (with the centering option off), am charged for it, but no object appears. I've tried lowering the ground under the point where the object was created in the hopes of unearthing it, but it doesn't appear to be underground. It doesn't appear to be anywhere. I'm not yet sure whether I'll be taxed for such objects, but I guess I'll find out soon.
Oh, and when rotating objects, if I try to enter a value into the 'X' field, often as not when I click outside the box to apply that new value, 'x' reverts to zero and instead 'z' is affected. Again, working primarily with cubes. If I use the rotation sphere and drag it into place instead, 'x' and 'z' are altered normally. The problem doesn't appear to apply to 'y'.
Hollow objects also do not appear to behave normally when stretched or shrunk as part of a group. I built a shell of a house and then discovered that the scale was slightly off, so tried to shrink it -- all of the wall panels that didn't contain windows, and all of the floors, shrunk beautifully, remaining perfectly in place relative to the neighobring pieces. Anything that was hollow -- windows, the curved cylinder-parts, etc. -- stuck out jaggedly. Don't know if this is intentional or not, but as long as I'm writing up, I figured I'd mention it. It's also irritating the way 'cut' objects work -- I have a few small wedges of cylinder, and a few half-cylinder pieces, but when selected their center is placed at where the cylinder would be if it were whole. A nitpick, I know, but perhaps that's part of why these types of objects aren't behaving like the rest.
Thanks -- it's a great game so far, and I'm enjoying it a lot, in spite of the big mess above.
