The rules of double strike?

[Carnac]

Can someone explain me the the rules of double strike in the following 3 scenarios?

Scenario 1: My opponent attacks with a 6/6 creature. I block with a 3/3 doublestrike creature. What happens? They both die, or...?

Scenario 2: My opponent attacks with a 6/6 creature. I block with a 3/3 doublestrike + firststrike creature. What happens? The 6/6 dies and 3/3 survives, or...?

Scenario 3: My opponent attacks with a 6/6 firststrike creature. I block with a 3/3 doublestrike + firststrike creature. What happens? They both die, or...?

Thanks in advance...

[Apollyon]

Double strike means that they deal damage during both first strike damage and regular damage. A creature with double strike gaining first strike does nothing.

Scenario 1: During first strike damage, the 3/3 deals 3 damage to the 6/6. During regular damage, the 3/3 deals 3 damage to the 6/6 and the 6/6 deals 6 damage to the 3/3. So after regular damage, you have a 6/6 with 6 damage and a 3/3 with 6 damage. Both die.

Scenario 2: Same as scenario 1.

Scenario 3: During first strike damage, the 3/3 deals 3 damage to the 6/6 and the 6/6 deals 6 damage to the 3/3. The 6/6 has 3 damage on him, and the 3/3 has 6 damage on him, so it dies.