That segment was simply awesome. It's unbelievable how well designed those original levels are despite being so difficult to design and edit. Can you imagine designing an entire level, only to realize that something about it broke the entire stage? That would be crazy considering how hard it was to fix things. These guys are legends.
What a very cool and informative video. I like how when they first started they would draw on a graphing paper. They've put much thought into creating levels for this iconic game, that's why it's so great. This new game will make budding game designers out of us.