Spinning 360 degrees, using Tween.Rotation is a bit unwieldy.

[octia]

Now, I might be wrong. But I think this is the easiest way to spin something 360 degrees, endlessly on loop.

Sequence s = Sequence.Create(-1, CycleMode.Restart, Ease.Linear);
s.Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -90f), rotationTime/4f))
    .Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -180f), rotationTime/4f))
    .Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -270f), rotationTime/4f))
    .Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -360f), rotationTime/4f));

Ideally, a single Tween.Rotation could achieve it, but to my knowledge, it cannot. Am I wrong?