I've had some time for the first rank and the last level today. I've attached the replays. 
For the written comments here I will focus on what could be improved.
In general:
My favorite level so far was 1 17!
As Nepster also stated: For my taste there were too many huge levels with 15+ builders. I would try turning down the builder count drastically and aim for a balance between small, medium and large levels in future content.
In quite a lot of levels I just had to build very long bridges where I just assigned a builder, pressed the skip 10secs button, assigned the next builder, pressed the skip 10secs button, assigned the next builder,......this makes some levels seem very monoton.
Level specific:
- 1 02 + 1 03: I think 5-10 lemmings would have done the trick here.
- 1 05: The empty space where you just walk could have been trimmed here. You have long walking periods where nothing needs to be assigned. You could have achieved the same with a much smaller level.
- 1 09: This is too hard and too long for a simple builder tutorial. I would have put the exit on the lower right side here.
- 1 12: This is quite a step in difficulty from the last level. Mining from below through a ceiling could easily be a road block for less experienced players.
- 1 13: I think I stated many times that I really don't like the disjoint union kind of levels.
Each section could have been a level on it's own.
- 1 17: A really good puzzle!
- 1 20: Exits should always be visible! Even more when they can't hide from true physics mode.
- 4 20: I see the main problem here should be "how to turn with just builders". But you could really cut the level height in half here and still make the level work with waaaaay less builders.
- 4 19: I quickly checked the level as Nepster stated that it may be impossible: I quicky saw a solution that failed to a terrain piece being 1 pixel off. Could you check if this level is indeed possible.

For the written comments here I will focus on what could be improved.
In general:
My favorite level so far was 1 17!

As Nepster also stated: For my taste there were too many huge levels with 15+ builders. I would try turning down the builder count drastically and aim for a balance between small, medium and large levels in future content.
In quite a lot of levels I just had to build very long bridges where I just assigned a builder, pressed the skip 10secs button, assigned the next builder, pressed the skip 10secs button, assigned the next builder,......this makes some levels seem very monoton.
Level specific:
Spoiler
- 1 02 + 1 03: I think 5-10 lemmings would have done the trick here.

- 1 05: The empty space where you just walk could have been trimmed here. You have long walking periods where nothing needs to be assigned. You could have achieved the same with a much smaller level.
- 1 09: This is too hard and too long for a simple builder tutorial. I would have put the exit on the lower right side here.
- 1 12: This is quite a step in difficulty from the last level. Mining from below through a ceiling could easily be a road block for less experienced players.
- 1 13: I think I stated many times that I really don't like the disjoint union kind of levels.

- 1 17: A really good puzzle!

- 1 20: Exits should always be visible! Even more when they can't hide from true physics mode.

- 4 20: I see the main problem here should be "how to turn with just builders". But you could really cut the level height in half here and still make the level work with waaaaay less builders.
- 4 19: I quickly checked the level as Nepster stated that it may be impossible: I quicky saw a solution that failed to a terrain piece being 1 pixel off. Could you check if this level is indeed possible.
