nspc Lv 1
The "ligand design" show us possibilities like "change atom" or "add a fragment".
When we click on them, it often says that "it is not possible".
A cool behavior can be to make impossible actions "gray".
So it is easy and faster to click on possible actions only.
(so we have not to test them all to find something possible)
We can keep possibility to click on "gray" buttons, to see the message that explains "why it is not possible"