hm well actually the bitcoin protocol enforces only 1 confirmation before a coin can be spent.
There's no such restriction, you can also spend coins with no confirmation, but they will not be included in the block right away.
that's what I meant. I consider a 0 confirmation transaction "not spent" and as you said a transaction can't get a confirmation before all its inputs have atleast 1 confirmation. And ofc you can send a transaction based on a 0 confirmation input I think that's what satoshi dice does to prevent double spendings.