How to “rotate” a layer/view (e.g. just like you would in enigmo)

float   angle = M_PI;  //rotate 180°, or 1 π radians
layer.transform = CATransform3DMakeRotation(angle, 0, 0.0, 1.0);

CGAffineTransform transform = CGAffineTransformMakeRotation(angle);
[[self viewWithTag:999] setTransform:transform];