For the precise glyphs, the two filled in ones seem to fit best. Of those two, I (slightly) prefer 
over 
, even though it seems to break the whole cube-voxel mentality. Some misc notes:
- outlines are going to be hard as a font (glyphs will have to be large on screen!)
- The x feels out of place
-
has more visually distinct things going on; I suspect it’d be easier recognize at a glance (if that’s a goal).
-
Is interesting for the same reason, but the square & elbow blend together too much.
-
- If you do end up going with right angles, put more margin between the different features so it doesn’t bleed together at small sizes!