if I move to the edge, I want the ship to stop right at the edge, rather than keep going off the screen.
Well, I think you can do something like:
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If => the player touches the edge of the layout :
Disable the ScrollTo behaviour.
Start a timer of 3 seconds (choose your timelapse) once.
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If => After the 3 seconds timer the player is still touching the edge of the layout:
Restart the 3 seconds timer once.
---
Else => Enable back the ScrollTo behaviours (to continue the automatic scrolling).
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My explanations above are NOT real code, I just to show you the visual of how to make your requested feature work.
By playing with the enable/disable ScrollTo behaviour, you can play/pause the automatic scrolling.
If you are asking why a timer of 3 seconds, it's because keeping checking the collision between the player and the edge of the layout can possibly be a problem if you had some physics stuff after. However, by adding a 3 seconds timer, you get a little cooldown to smoothly resume the ScrollTo behaviour.
This is how I would do it. Depend on your needs.