Constraints are the little red lines that you see between sections of a backbone. Though these usually go away with a simple wiggle, occasionally they are bit more persistent. Constraints can be thought of as predetermined rubber bands in a way. They are used to show sections of the puzzle that should be close to one another.
Sometimes on a puzzle there will be one or two which simply will not go away on their own. Though infrequent, they are quite troublesome. A visible constraint may reduce your score by 100 points or more. It is in your best interest to do all within your power to eradicate them from your puzzle. Normally even persistent ones will go away before mid-game, however for those that do not a couple of effective strategies for removing them are as follows:
- Try tracing them with a rubber band. Sometimes all they need is a little extra incentive to push themselves where they need to go. Once you have the band(s) over the constraint, wiggle. If the constraint does not go away, try working as normal for a little while, leaving the bands in place.
- Try pushing the sidechains in the immediate vicinity of the constraint around a bit. Make them clash with one another, or pull them as far away from the constraint line as possible. Wiggle it out again, and see if it goes away.
- If the banding and sidechain techniques do not work, sometimes it is helpful to look at the backbone structure of the section with constraints. If the section in question is a loop, it can be helpful to change it to a helix, and use the straighten and rotate tools to contort it where it should be. If the segment is folded over on itself, changing it to a sheet and straightening it may cure the problem. If the segment is already one of these two, than these tools should also be effective at removing the constraint.
- Finally, if you simply cannot remove the constraint, you may wish to consider ignoring it for a while. Focus on the rest of the puzzle, often through working the backbone, the constraint will disappear on it's own. Just keep in mind while it is there, that it is generally an indicator of a section of the backbone being out of place.
Contrainsts at leat in puzzle 480 are harmonic constraints :