How can I use my Apple Card for games if it wants a credit card?

The credit or debit card is used as a backup payment method and also proof of age for the purchase, rental or subscription of age restricted content. The primary funding source will be the gift card and the backup payment method is only charged if the balance due exceeded the funds on the gift card/

If you want to purchase age restricted content (including games) then you’ll need to add a credit or debit card.

I can’t use my card for a game