How does the trail work?

[Tsuki Zero]

I see star marks in it changing quantity and placement as I change shots into comet or meteor, but do not see how those helps.

[MBRedboy31]

The star marks estimate how far the ball will travel at different marks of the power bar, assuming that the ball is only traveling over regular terrain and there isn't anything else in the way that would affect the ball's speed. For example, if you shoot the ball when the power level is at 2 bars, the ball will travel to the second star on the trail.

When you change the temperature, the stars' spacing is changed to reflect the change in ball friction. Full meteor makes the ball go a short distance on regular terrain, so the stars are placed close together, while full comet makes the ball go a long distance on regular terrain, so the stars are placed further apart.

Notably, half meteor has the same effectiveness on both normal and rough terrain, so it's the only temperature where the stars are reliable when rough terrain is involved.