Repeating something creates a pattern. Changing it slightly keeps the pattern interesting. Good design uses both.
Repetition creates unity. Repeated shapes, colors or spacing tie a design together and are easy for the eye to follow. The stars in our worlds are a few repeated dots.
Too much repetition gets dull. A perfectly even pattern stops holding attention. Each of our stars blinks slightly out of step with the others, which keeps the sky from looking mechanical.
Ways to vary. You can change size, color, spacing or angle. Size changes suggest depth, color changes suggest mood, and uneven spacing creates rhythm.
Spacing changes the effect. Tightly packed repeats read as a texture. Widely spaced repeats read as individual items you can count.
Gradual change tells a story. When each repeat changes a little in the same direction, like getting bigger or darker, the pattern suggests movement or growth.
Try it: look at the World Directory on the left. Every row has the same shape, a colored square and a world name, and only the color and name change.