If you draw a perfect circle, then measure its diameter, measure its circumference, divide circumference by diameter, you get PI, always. 

There's no intelligent design there, it just IS, it's fact, it's math, a circle is defined as an 2d object where the diameter is the same measured from any edge to another passing through the center, no intelligence, no magic, just math.

Just as 1+1 = 2, no intelligence, it just is.

If these facts are true, and there are other facts that ring true regardless of circumstance, then you have solid building blocks for a complex system without design.