sperate colonizable types!

[keller]

The thing is , in every great 4x game the types of planets that you can colonize is divided into different research areas but in Horizon once you get terraforming you can colonize every type of planet.
Now this can seriously imbalance the game for any race that gets this tech no matter how small or big they already are. Therefore, I would like to suggest breaking this up a little and that once terraforming is discovered that an additional area underneath the bio section appears which allows you to choose what type of planets you wish to research to become colonizable. It would be just like any other area of research meaning you would have the ability to concentrate on one type of planet or all of them at the same time. Each new level increases the amount of the planet that you can use. For example humans (who use terra type planets) research area would look like this:

current level
colonize barren 1 (10% usable)
colonize arctic 1 (10% usable)
colonize desert 1 (10% usable)
colonize volcanic 0
colonize toxic 0
colonize terran 10 ( 100% usable)
colonize gas giants 0

[Xyquas]

The thing is , in every great 4x game the types of planets that you can colonize is divided into different research areas

That's wrong. In all time classic MOO2 there was exactly the same approach. You just needed a radiation shield to be built on contaminated planets to make them barren. This equals to Horizon's toxic planets which need to be cleaned up before terraforming (which I find a very cool idea btw). And in Birth Of The Federation you didn't need different techs either. Actually, I think there was no tech needed though I couldn't swear because it's been too long I played it the last time.

Therefore, I would like to suggest breaking this up a little and that once terraforming is discovered that an additional area underneath the bio section appears which allows you to choose what type of planets you wish to research to become colonizable.

I always found this approach extremely artificial. I understand terraforming as being able to control climate, atmosphere and biology which are general principles. It just does not make sense in any way to me if I understand those principles why they should apply to one planet type only.
So I vote for: Leave terraforming exactly like it is.