There is no need to draw up a scientific experiment to prove God's existence.
Everything everywhere shows purpose, intent, and design.
All of creation shows it.
You couldn't, you wouldn't logically look at your computer screen and say this happened by chance. No, of course not. It is proof that the factories and various processes required to make your screen exist out there. Yet your computer screen is vastly more simple in its functioning than even a single cell in your vast body of organs!
Look at even a single cell. Look at even a single strand of DNA from a single creature. Then consider how all the cells in the body work together. Think about your eyeball looking at this screen right now.
Weird coincidence or design? You be the judge. And when I say "look", I really mean "see".
We can't say that our own will is responsible for our selecting our features, because we were not around at the time of our making to select anything. Another will has done all this, not our own.
No matter how hard I could desire it, I can not even change a single cell in my own body. If my desire can not induce change via evolution then who make me?
It has to be God. It is only God...with one exception...corrupted creation.
We see good intent out there in creation; however, we also see many creations that have been bent on destruction of other creations. Mosquitoes for example, although the males suck fruit the females during their reproductive time suck blood, spreading disease and killing too many people to count (like many other corrupted creations such as viruses and parasites and others). Most Christians believe, that these creations that use to serve a useful purpose, have turned bad because some thing or someone (evil spirits) messed with their DNA changing them into what they are today. They got redesigned from good to bad. Yet their clever design still proves intent! For when God was done creating everything, the Bible tells us, "He saw that it was good". And in a parable in the Bible, He is asked "where then did the weeds come from?" "An enemy has done this." He replied.
So then, God the creator is good, just as the Bible says.
And His enemies, who can not create anything themselves, do have limited power to redesign particular good designs. So then God made eyes and God made worms, but He did not make eye worms, but his enemies did.
His enemies are limited. God is not limited. He is leaving everything to grow together so that He will not judge the weeds along with the wheat. But at the end of the age, he will rescue the wheat and gather the weeds to burn. Justice will finally reign forever, and everything evil will finally be destroyed.