A manual calculate button for the bigger puzzles would be nice.

Just so it doesn’t pause for a couple seconds after every mutation, obviously not the highest priority, but I heard some requests in chat and thought it was a good idea. I would guess it wouldn’t be too hard to add given that it most likely makes a call to recalcuate after laying down each mutation, but then again I haven’t seen the code.

This is a really interesting idea.

I have put it on our feature tracker as #379.

Thanks for bringing up this idea!

Yes, this would be a big improvement for the game-like features of ETERNA. It is annoying to have to wait between adding halves of pairs, for instance. And at the beginning of a puzzle, the graphics for additions and calculations slow things down too much. Maybe this could be a button you hold down to suspend calculations until you are ready.
Another suggestion to make ETERNA more game-like would be to have all the screen functions have keyboard shortcuts, that could be accessed one-handed. The Undo being Z on the other side of the keyboard from the numeric functions isn’t optimal. Or am I missing something? Many video games have an ergonomic function at set-up that allows you to set things for yourself so both right- and left-handed mousers can use the mouse in one hand and modify its function with the other. I’m left-handed so I tend to see these things possibly more than the right-handed majority.
It would also be nice to have a Previous function, which could then allow you to toggle between 2 functions. ETERNA is probably most interested in the scientific aspects of the game, but I think adding things like this in and making it more ergonomic would make it much easier for me to spend vast amounts of time doing it. Win/win.

Alternatively you could have the recalculate delay starting for some interval, say a constant factor plus some multiple of the last recalculate time. If no changes are made in that time period the recalculate runs. Say try 0.05 + 2.0*T to start. If it took 0.6s to do the last recalculate, the next recalculate would occur no sooner than 1.25s after the last change operation. A sufficiently long pause in editing the structure would cause a recalculation, but a quick succession of changes would delay the next recalculate, and smaller puzzles would automatically get faster turnaround.