I am currently working through the book and just finished up chapter 4. While completing the program throughout the project I ran into a lot of issues with constraints in interface builder. I had a lot of issues getting the button to draw correctly when overlapping the switches. In addition, the switches kept bouncing above the toggle control. I managed to work my way through them but I wondered if other folks had similar problems? I also am wondering what the significance of the purple constraints (purple icon in the dock view) versus the blue ones. I seem to be unable to delete the purple constraints but the blue ones I was able to remove to clear up my alignment issues. I guess I am thinking how do you keep these "clean" so as to not cause UI issues when altering a XIB for changes in the future? Lastly, and this is just a general query, does anyone know if there are settings to turn on the guidelines in interface builder? My margin dotted line shown throughout the chapter is not displaying (wondering if a setting got bumped off somewhere). Thanks in advance for anyone who answers. So far I am really enjoying the book.