drag pan map, including cells
shift-drag move cell grid relative to map
option-drag rotate cell grid about map centre
mouse wheel zoom map, including cells
shift-mouse wheel zoom cells relative to map (sizes 0 to 8)
space hide/unhide map
escape temporarily hide cells (while pressed)
E hide/unhide empty cells
S or H square/hexagonal cells
0 to 8 set number of web workers (default=8)