Looking for a deep learning book posted on HN several months ago

I few months ago, an online book introducing deep learning with was posted to HN. I thought I had bookmarked it, but I guess I didn't.

I remember the book being excellent - containing both theoretical rigor along with practical from-scratch implementations using what I believe were several frameworks (I remember Pytorch being one of them). In the introduction, the book compared itself "Deep Learning" by Courville, Goodfellow and Bengio but with the addition of practical coding examples without sacrificing the theoretical rigor. I would say the explicit goal of the authors was to essentially add coding examples to the "Deep Learning" textbook.

This was not a "cookbook"- style book, but a book that was designed for serious practitioners who wanted to be able understand what was going on under the hood and to be able to roll their own implementations eventually. Subsequent Google searches have come up with only cookbook after cookbook.

Does anybody remember this book or know of it?

Thanks in advance.