[Fester Chugabrew]

Proof of purposeful and intricate design is proof of a Designer.

That's going a bit far, insofar as you use the word "proof." Evidence, yes. Proof? No.

[PapaNew]

Evidence is considered proof in a court of law if the evidence for proof is clear and convincing, a preponderance, or leaves no reasonable doubt about a conclusion.

Just as the existence of a car is proof beyond a reasonable doubt of a designer of that car, so your body is proof beyond a reasonable doubt that Someone designed you.