When it comes to level design you want to plan every little detail fit well with gameplay mechanics. You can plan it only with level layouts. Level layout based on prototype gameplay but it doesn't mean that gameplay element won't change or even being removed - prototyped gameplay give you something to start from but that's it.
I watched Chair's GDC Presentation (about Shadow Complex) and I decided to keep that approach for level design of Circulation.
So I started to sketch levels for Circulation with pen and paper. I sketched each level in a day or two.
That drawing was just a rough ideas of levels and mechanics, they doesn't quite match with gameplay units (jump height, lenght, speed, etc.) because I wasn't sure what unit numbers was fun, so there's no documented units yet.
Illustrator Level Layout
After tests on paper I begin to recreating levels in Adobe Illustrator. I begin testing units in game and Illustrator and come up with decent numbers. In Illustrator I set up grids and grid snapping and began laying out all levels. While doing that I redesigned many parts and remove even more. In Illustrator it was a lot easier that doing on paper.
After laying out levels we started testing them in Illustrator. Our game is about exploration so gameplay representation in Illustrator was just fine.
Illustrator laying out and testing levels in early stages of development brings decisions flexibility and can save big amount of time or even can save you from redoing a lot of work.
Only when we tested our levels in Illustrator and we saw that all was quite fine and dandy, we can finally jump in Unreal Editor and start blocking levels with BSP brushes. Andrew did it very quickly and we start testing actual gameplay in existing levels.
When BSP Blockout was done we started placing gameplay elements and placeholders for story, cinematics and so on. Idea behind it was when we're done with all gameplay-related stuff and test it, we can focus on sedondary tasks like placing cameras, events and puzzles.