Symmetry refers to the ways in which a pattern or image repeats itself. Symmetries are all around us in nature, art, architecture, and even in day-to-day objects that we purchase in a store. Symmetric objects have an esthetic appeal; they are attractive and pleasing to the eye.

Frieze Patterns	Molecular structure of porphyrazin
Dome of the Rock	a wallpaper pattern

Below is an incomplete sampling of websites that explain and give examples of symmetries:

	int w = 15 int h = 10; rect(0,10,w,h); rect(20,10,w,h); rect(40,10,w,h); rect(60,10,w,h); rect(80,10,w,h);	One way to repeat rectangle shapes is to simply repeat the code.
	However, this could get very cumbersome if we wanted a lot of rectangles!
	size(100,100); int w = 10; int h = 50; for (int i=0; i < 6; i++) {   rect(15*i,0, w, h); }	Instead, we use a structure called a loop. One type of loop is called a for-loop. An example is shown here on the left. The body of the for-loop is repeated 6 times with the "loop-variable" i changing from 0 to 5. Recall that the syntax for a rectangle is rect(x,y,w,h) where x is the x-coordinate of the upper left corner. In this loop the x-coordinate changes from 0*15, 1*15,... 5*15 resulting in a row of rectangles. The variable i can be used to change any other characteristic you want. See below for more examples.

noFill(); for (int i=0; i < 10; i++) { rect(0,0, i*10, i*10); }	for (int i=10; i >= 0; i--) { fill(i*25,0,255); rect(0,0, i*10, i*10); }	background(0,0,0); for (int i=10; i >= 0; i--) { stroke(i*25,255,0); line(0,0, 100-i*10, i*10); ellipse(100-i*10, i*10,10,10); }