This was awesome! While perhaps bordering on being a skinner-box, I also think that was the point ;D A great use of the theme. It made me very nostalgic for those sorts of games, and was thinking if this was a mobile game, I might sink a lot more time on it than I'd like (or not, would be a fun "check notifications and feed/bathe the pet").
I think the one thing it needs is something to shake it up a little. Some unexpected or random events, or changing mechanics at higher ages. Once I had a good flow setup it was very easy to keep my pet happy at max stats and still have my intensity always increasing overall. Perhaps adding either something like the pet's stats decrease faster as it ages, or some random events can occur (such, "you're pet is sick! it's stats decrease "x" times as fast for "y" periods until you buy medicine for "zzzz" intensity!). Or just some sort of currency/intensity sink.
Absolutely loved the visual style, and I like how you refer to it as "mining" ;D Extremely well done!