In what way is "A Midsummer Night's Dream" a play full of pattern and design?

Another way to look at this concept is the plot within a plot design.  We have several plots in this play.  One is Titania and Oberon's fight over a young servant boy.  Another is the young lovers' troubles (Lysander, Demetrius, Hermia, and Helena).  You also have the love story of Hippolyta and Theseus.  Another is the artisans story, with Bottom, Snug, Peter Quince, and the rest.  Finally, you also have the play within a play with the love story of Thisbe and Pyramus, which mirrors Romeo and Juliet in many ways!  All of these plots make the story very unique, complicated, yet endearing and funny. 

You can look at it as all of the subplots circling around the main plot of the young lovers.  The main action centers around them; yet, the subplots are also connected to them in one way or another.

Another aspect of patterns and design is the focus on the fairy world, on the one hand, and the mortal world on the other.  The play not only mingles the subplots, it mixes the mortal worlds and fairy worlds.