This game has some severe problems, it bluescreened my computer once, and bogged it down another time. Other than that, it's not very hard, as others said, it's mostly luck.
Finally beat it at level 79... too bad I wasn't level 78 when beating level 78... oh well. I feel like the last 15 levels didn't really make my guy that much better, though. Anyway, fun enough that I stuck with it to the end...
Getting 6000 was never a huge problem for me... but it took a while to trim my time to under 18 days... started getting hard for me to beat it under 22 or so, but with some practice I just got it in 17! badge for me!
For those of you who are having a hard time with the challenge... or for that matter, most of the rest of the game, remember that simpler is better. A complicated bridge structure weighs a lot more than a simple one, and is much more likely to collapse under its own weight...
I think there should be an easier way to delete beams than clicking the button- keyboard shortcuts are my friend. or similarly, to be able to select beams by sweeping over them instead of clicking exactly on them (a la starcraft selection). Am I just missing something? Regardless of these shortcomings, this game is really fun!