Drag a box to select. Click grabs one colour run.
Shift adds. A all, Alt+A none. Arrows nudge,
PgUp/PgDn for Z.
Tools only affect the selection.
Height
z 0
Edit
Placement
Blocks are offsets from the pivot. Keep original holds the offset the file
opened with. From bounds recomputes it.
Guides
Front faces -Y. +X+Y.
Optimise
Removes blocks you cannot see.
Model
No file loaded
Controls
Drag the model to use the tool, drag off it to orbit.
Middle-drag orbits round the block under it.
Shift+middle or right-drag pans, wheel zooms. Ctrl+middle focuses a block. Shift-click samples a colour. 1-6 tools, Ctrl+Z / Ctrl+Y.