I'm messing with an old Tamagotchi idea in a new way. There's a bunch of loops. You start with a critter in their tiny form.
1. To feed them, you play a matching game and keep all the ingredients that you match. The game is a faucet for materials, but you can only play a few times before you have to pay.
2. But the character likes some flavors better than others. You can craft foods together to make dishes that they like.
3. this is important because the contents of the food will affect how they grow up. Too much sugar will make them fat, more protein will make them strong.
4. There's another way. You can praise/scold them into doing what you want, but that will also affect their behavior and who they become. Too much scolding and they'll become a rebel and be harder to deal with. Too much praise they might become spoiled.
5. You can also buy them stuff for their room. or clothes to wear that will impact their happiness. They develop a certain style and that will change as they age.
6. Food goes bad, so you have to use it or lose it, but you can sell it, and there's a mart to buy stuff you want.
7. you can also trade with friends, so if they have things your character needs, you can swap
I think I can add regionality too, so like different places get different raw materials to encourage more trading and person to person interaction.
Maybe gearing closer to combat but after this feels stable, I'd add activities. Maybe a race, wrestling, archery, and art for speed, strength, dexterity and creativity. There should be single player and multiplayer options for these.