markmadras wrote: Welding
Is this when two elements overlap without a join at the node so the connection slides but no dark force occurs
Yes, that is welding, but dark force DOES occur in many configurations that include welding. At least that is my opinion. Many discussions have been made on the subject of whether welding creates force, and personally I am in no doubt that it can and does. The problem is that it doesn't always create force so it's incredibly difficult to make a ruling on it.
I asked if Ioncorpse had used welding because my own 760 solution only just had enough force to succeed (without welding) so I suspected some welding was being employed to create the extra force. I've included an example level that shows clearly the dark force that can be created from welding, but even in this configuration we still call it light. Why? Don't ask me, I even argued for it to be made dark. I guess it's too difficult to clearly define a difference between welding that does create force and welding that doesn't, and to ban all welding would severely limit creativity in light solutions.
Edit: Just added a second file that prevents the force from being so active, mainly for comparison. When welding tries to push a node into another object it can create very high force as shown in the "Welding Dark Force" file. But limit how much the node can penetrate and things act more naturally. But even in the second file, there is still a little force being created, yet compare the ammount of extra weight I added to the left side and the ball weight still easily tips it to the right as expected unlike the first example where dark force is clearly evident.