In this case, a simple random black rectangle on top of blank canvas.
You're shown two random ones.
Keep voting for the one you think that you like more, and you'll be training a neural net to help decide for a better one over time.
Often, we might not know which are all the rules that make us like a piece more than another, but with this method, you don't need to know...just have to keep voting and it'll be used as training data to train a simple neural net (using brain.js Javascript Library) on the page.
and over time it gets better at acting as you (or like you would vote) and each time you click generate() it can act as you and vote like 1000 times (after giving enough real votes of course).
program page:
https://thelotteryforum.com/braint.htmlYoutube demo after my 300 votes or so.