Fun is your brain rewarding you for something it thinks is practice on a useful skill. You get bored once you mastered it enough.

Some people continue playing a game even when it stops being fun, they are addicted to the reward mechanism in the game, and now the brain thinks that playing the game is a good way to work and provide for itself. I don't call that "play", its work, just not productive work.

Why is dice fun? Because your brain wants to map the pattern of the dice, trying to figure out how to get good rolls. You see that in most dice players, they develop a lot of superstition about what is good and bad dice, or how they always roll bad in critical moments etc. I'd assume that is from nature where you try to figure out what is a good nut to crack or where to find prey etc, basically a way to figure out useful patterns from random events.

It's probably not something you secretly wish when playing, and perhaps for the best (that you don't have fun and enjoy things always with an ulterior motive, except enjoying the experiences). I guess he's saying in the sense of the natural function of play, and we playing is mostly a consequence of the natural function. It's also very much true that we learn a lot, perhaps a significant chunk of what we learn is through play[1], so it's also undeniable that we do learn from play, even if humans have this great gift -- we are able to understand the nature of things (such as play) and choose to do them just for the sake of experiences, fun, joy, happiness, etc..

Which we should (finally :) ) recognize to be the source of all meaning.

We still should learn (and do practical stuff in general) because it supports our inner lives, including building technology, producing things (buildings, infrastructure) that support us and indeed enables our (inner) lives.

[1] Also of note humans, unlike LLMs, can learn all the time, we don't have a hard "training phase". It's true brain plasticity decays, and it becomes harder to learn as we age, but we can still learn more or less quickly at any age. This is why dedicating childhood to learning (as well as play) is natural.

Yes, evolution makes play fun, but it's really learning, in the same that that evolution has made sweet and fatty things extra tasty, because they are full of energy.

Jokes on you. Every time you played ball you were secretly learning about ballistic trajectories and estimating velocities using visual cues such as apparent angular size and parallax.