Recently, a friend of mine recommended "BabySparks", an app providing a set of development milestones and targeted growth activities for babies and toddlers.

This feels like the sort of thing I should be able to pull from a few books, rather than a subscription-based app. I'm also not particularly interested in Yet Another App, nor am I particularly keen on handing my infant's personal data to Yet Another Social Media company.

I'm especially interested in understanding the varying stages of development, and in activities to perform with aforementioned infant during their first year.

So: Any non-app resources that LessWrongers would care to recommend?