Slay the Spire: an amazing rogue lite deck builder. Similar to games like magic the gathering, but instead of going in with a deck, you get to add a card after each fight (or skip this, which is often the best choice).

It requires :

• doing some basic calculations during fights (should I spend all my energy on attacks this turn because I can beat this enemy now, or should I spend some energy on defense instead)
• experimenting with card effects and synergies between cards, and between cards and relics (small perma buffs you get during a run)
• at a higher level, having a macro plan of what challenge is ahead of you and what kind of cards you should pick to face them (pick attacks early on, then pivot to more defense once your damage is there)

It might be slightly too hard for an 8 yo though.

Alternatively, consider Wingspan. I play the physical game with my 8yo with no issue. It’s a score optimization game with beautiful illustrations of birds.