Anya and I came up with a new card game — sum war. It’s a bit like war, but you throw two cards. The person with the higher sum wins all of the cards & puts them on the bottom of their stack. Keep going until someone has all of the cards. There’s obviously lots of addition involved, but the game uses estimation too (I have a 5 and a 7, you have a 5 and a 9 … you win without actually adding anything).