Greetings.  I'm new here.  I've played through World of Goo and absolutely loved it.  I bought it on the Wii and completed it, but one level made me purchase the PC version because I thought it would make the OCD for that level much easier, as well as placement of the goos more accurate using a mouse rather than a Wiimote.

Well, I was wrong about making that level easier.  Chapter 4 - Bulletin Board System, as you can tell by the topic title, is the level in question.  This is by far the most frustrating level ever.  Trying to get OCD on here is horrible because of the randomness of the goos' flight paths.  Has anyone figured out why this is?  I have a few theories:

1. Mass of goo balls - I have noticed that the balls are different sizes.  I thought maybe this affected how they fly, but it appears this is not true.  I have seen the small ones both rocket off the structure and flop, when using the exact same angle (I have an aiming point that works about 90% of the time).  So this is not the reason.

2. Structure woble - This is another possibility.  The wobble of the structure affects the starting point of the goo and thus would alter the angle slightly.  However, the slight variations (they are very slight) would only affect the trajectory significantly if the flight path was over a vast distance, which in this case, it is not.  Still, something to consider.

3.  Windage - This is my leading theory, but my observations haven't yeilded any results.  It was always my main concern, however I cannot detect any variations in the wind.  Anyone who can provide more information on this would be greatly appreciated.

4.  Pull - The amount of pull obviously affects the distance it will go, but is it to a certain extent?  Once you can't pull the arrow any further, it that the max power you can put on it, or does it continue past the length of the arrow?  Haven't seen much evidence of this, and it's very unlikely.

5. Luck - I hate this theory, because I am not a lucky person, but it's still worth considering.  I have gotten close to getting all the goos past those gears, spending nearly 30 minutes to find the right angle, windage, and for the structure to be completely still, only to have one goo ball rocket off the structure for no apparent reason, thus dying in the gears.  If it's just because I'm an unlucky person and this goo ball just happened to get the rocket start randomly assigned to it, then I will never get this OCD.

If anyone can help with this analysis, I would greatly appreciate it.  This level has provided an endless amount of frustration.  Flops and rocket starts alike are killing me and I want it to stop.  However, if it's beyond my control, then this is one level that shall be bare of flags.

Thank you and God bless.

Actually Bulletin have almost fail proof method.

Generally, if you want to shoot to the exact same spot every time, do the followig:
1) Click on a ball
2) Draw the cursor until you reach the screen's top left
3) Make sure the screen is zoomed out (When you look away from the ball it zooms back)
At this point, your shot is absolute - it is at max power, and if you can shoot to the exact same spot every time.

But apparently this is not enough.
The problem is that when shooting from a corner of a structure, you cant know for sure if the ball is on the top edge or the right edge.
Therefore sometimes it will shoot as if it was shot from the top edge and sometimes as if it was shot from the right edge.
So in order to make your shots as accurate as you can, always shoot from the middle of the right edge.

hope it helped :)

I got it.  There was something I wasn't taking into consideration (because I didn't think it should have mattered), but upon reading and re-reading your post, I finally figured out what was going on and what I wasn't considering; the edge it was being launched from.  When you mentioned "always shoot from the right edge", I initially thought you meant just for that particular structure.  Then, after a second trial (I re-adjusted my aiming point to the middle of the edge AFTER the fourth vector of the overhanging structure), I finally managed to get all the balls through.  I thought I was home-free, but cleared my mind, reminding myself it wasn't over yet, even if the last part was super easy.  Turns out I was right, because something really stupid happened.  I grabbed a ball and launched it, and it slingshot right around the gear, just like it always does for me.  The second, however, made me want to chuck my monitor out the window (no worries, I have two monitors and I live on the first floor, it probably would have survived  XD) when it just flopped right into the gear.  WTF??  A third trial, and the last ball from the first structure flopped and hit the corner edge of the ground right next to the second structure and got stuck there.  That's when your statement made sense.  The edge it was being launched from did have some kind of effect, which I tested immediately.  From the first structure to the second, balls launched from the bottom edge, aimed just right of the top-right vector of the second structure, lobbed nicely onto the structure, but when launched from the right edge, aimed at the same spot, tried to fly straight, usually landing near or on the corner of the floor.  Why the edge has an effect, I don't know, but at least I know it does.

Now I have OCD +1 on that stage and it will never be played again.  You've been an immense help.  My monitor and I thank you.

Anytime  :)
Keep in mind that you can get 15 balls in that stage :)
http://2dboy.com/forum/index.php/topic,1281.0.html