Why does the research Concrete Productivity 3 require Concrete Productivity 1 instead of Concrete Productivity 2? Also shouldn't the infinity research only require Concrete Productivity 3? Not counting the science pack researches needed, of course.

Once you get to the infinity research it doesn't matter, but I was just curious.

I think I did it this way because productivity 2 and 3 are meant to be researched in parallel, depending on wether you went for purple science first or yellow science first. The game allows you to get yellow or purple in whatever order you want, so I applied that same game philosophy here.

I just thought that each research would require the previous research, which is how the game handled all researches with more than 1 level.