[CATransaction begin];
[CATransaction setAnimationDuration:5];
CGAffineTransform currentTransform = squareLayer.affineTransform;
CGFloat angle = M_PI;
squareLayer.affineTransform = CGAffineTransformRotate(currentTransform, angle);
[CATransaction commit];
と
[CATransaction begin];
[CATransaction setAnimationDuration:5];
CGAffineTransform currentTransform = squareLayer.affineTransform;
CGFloat angle = (M_PI * -1);
squareLayer.affineTransform = CGAffineTransformRotate(currentTransform, angle);
[CATransaction commit];
私は -1 が方向を逆にしたと思ったでしょうが、どうやらそうではありませんか?