subview addShape + mask not quite sure what to do with this but it looks cool.

C4Workspace.m

//
//  C4WorkSpace.m
//  Examples
//
//  Created by Greg Debicki.
//

@implementation C4WorkSpace {
    C4Shape *s1, *s2, *m;
}

-(void)setup {
    
    [self setupShapes];
    
    m.mask = s1;
    
    [s1 addShape:s2];
    [self.canvas addShape:m];
}

-(void)setupShapes {
    m = [C4Shape ellipse:CGRectMake(0, 0, 300, 300)];
    s1 = [C4Shape rect:CGRectMake(0, 0, m.height*2, m.height/5)];
    s2 = [C4Shape rect:CGRectMake(0, 0, m.height/5, m.height*2)];
    
    m.center = self.canvas.center;
    s1.center = CGPointMake(m.width/2 ,m.height/2);
    s2.center = CGPointMake(s1.width/2 ,s1.height/2);
    
    m.lineWidth = 10;
    m.fillColor = [UIColor clearColor];
    
    s1.animationDuration = 1.71f;
    s1.rotation -= PI;
    s1.animationOptions = REPEAT;
    s2.animationDuration = 2.23f;
    s2.rotation += TWO_PI;
    s2.animationOptions = REPEAT | AUTOREVERSE;
}


@end