Controls
Paint Cell - left mouse button (LMB).
Cross out Cell - right mouse button (RMB), or Shift + LMB for Opera.
Paint Group of Cells - LMB + moving. The same is to cross out a group of cells, but with RMB.
Cross out Number - LMB or RMB.
Show Color Panel - middle mouse button, or Ctrl + LMB for Opera.
In Opera and other browsers you can turn off "gestures", then RMB will become available.
HotKeys
- Ctrl + S - Save
- Ctrl + Z - Undo
- Ctrl + Y - Redo