The production progress bar in general is obviously great, but what does it mean in the context of projects like birth rate enhancement or wealth? By the way, I like the projects !

In the mouse over and on the planet list I sometimes see the progress bar for projects partially or fully filled what does that mean?

I would recommend to keep the bar always filled for projects, but color code it differently to indicate that this job is endless.

In case you encounter a precursor Builder - which usually finishes the current production at the nearest planet - what does it do to a project?

Should the precursor Builders be applied to another planet and not to the planet building a project?

I would prefer that, instead of the message that the precursor Builders tried to finish your project which it currently says, but I do not think it does much, does it ?  

Leaves the question open what the effect is, if all planets run a  project ... ? On that I would give some wealth for having sold the precursor Builders.

(Unless you want to add the ability to store goodies like the precursor builders and therefore enable the player to use them at his choice. (Could be solved by making it into a ship that can travel to any planet at some decent speed and when it is applied to the planet it finishes the current production (like an engineer in another well known game).