Thanks!
Glad you like the scenery; I'm not always happy with the graphics I produce but there were some areas of this that I was really happy with. Level 4 (the pipes area) was originally going to have a background made with the grey version of the tileset used in Levels 6 and 2, but I was using the gradient I settled on while building tilesets and decided that it suited much better; I like how the lightness of the area contrasts with the darkness of the previous areas, which suits the mood of the area well; I wanted that level to feel safer, to give a chance to get your breath back after the intensity of the previous few sequences.
I really loved the tangled vegetation I used in Level 3, especially where it grows over robots, doors and consoles. The screen with the overgrown ball-spewer (I think it's the second screen of the area) is, in my opinion, one of the best screens I've ever produced.
I think Level 2 looked great too; the very detailed background, with the greyish vegetation, was a good contrast with the featureless foreground, which gave more of a feel of desolation and abandonment than I personally could have achieved with detail.
Those two are my personal favourite levels in terms of graphics alone. My very favourite area was the place between Levels 6 and 5, with the atmosphere and very... delicate story-telling.
As for the chaser area, I originally paced it very tensely. Then, just before I sent it to be tested, I challenged myself to play through it and pause for about 1 second as I entered each screen. I had to move a lot of enemies to do it.
Lesson learnt!