For the longest time I thought the puzzles with more than one laser/target needed to all be lit up at the same time in order to be completed. I spent the longest time on one and then it suddenly completed in this state:
After that it was pretty simple, knowing I only needed to hit one sphere at a time. Strangely the final area unlocked when I'd only gotten three out of four lights done in the ceiling puzzle, I was on my way trying to find the source of the fourth laser (the blue one, I think) when I saw the glowing disc and got teleported inside. Was the ceiling puzzle a bonus, secret thing?
I liked being able to run around extremely fast. :)