user12629: I've recently played some games as Black that opened like this:
[White "Opponent"]
[Black "Me"]
[Result "*"]
[ECO "B01"]
[FEN ""]
[CurrentPosition "rnb1kbnr/ppp1pppp/8/3q4/2P5/8/PP1P1PPP/RNBQKBNR b KQkq c3 0 3"]

1.e4 d5 2.exd5 Qxd5 3.c4  *

c4 seems to be a very uncommon move as opposed to Nc3.  But it doesn't seem bad at first glance - it allows the knight to go behind the pawn when Nc3 is later played, and grabs some central/queenside space.  It also forces the queen to move (although 3.Nc3 would also have done that.)
How do I refute this variation?  Or is it perfectly playable?
My opponent and I both have USCF ratings in the 1500s, if that matters.

user-1: As suggested by @FredKnight, I would play 3...Qe4+
[FEN ""]
[StartPly "5"]

1. e4 d5 2. exd5 Qxd5 3. c4 Qe4+ 4. Qe2 (4. Be2 Qxg2 5. Bf3 Qg6) Qxe2+ 5. Bxe2 c5

In the final position:

White's b- and d-pawns are restrained
Although White has developed the bishop, it is not a good piece yet

I think the evaluation is dynamic equality here.

user12449: This is what I try to accomplish as white, but I play Nf3 first.
Although your can't take advantage this early, there are good moves depending on your temperament.
Qe4+ forces Qe2, else a pawn hangs, and the trade of queens.
Qa5 pins the d-pawn which gives you the opportunity to get in c5 (e5 is more drawish) and get a central majority.
With a normal game continuation, that is Qa5 => Nf6..., the d-pawn is slightly weaker as white can't play c3 to support it.  
Just the opinion of a 2000 player.

12629: <p>I've recently played some games as Black that opened like this:</p>

<pre><code>[White "Opponent"]
[Black "Me"]
[Result "*"]
[ECO "B01"]
[FEN ""]
[CurrentPosition "rnb1kbnr/ppp1pppp/8/3q4/2P5/8/PP1P1PPP/RNBQKBNR b KQkq c3 0 3"]

1.e4 d5 2.exd5 Qxd5 3.c4  *
</code></pre>

<p>c4 seems to be a very uncommon move as opposed to Nc3.  But it doesn't seem bad at first glance - it allows the knight to go behind the pawn when Nc3 is later played, and grabs some central/queenside space.  It also forces the queen to move (although 3.Nc3 would also have done that.)</p>

<p>How do I refute this variation?  Or is it perfectly playable?</p>

<p>My opponent and I both have USCF ratings in the 1500s, if that matters.</p>
 -1: <p>As suggested by @FredKnight, I would play 3...Qe4+</p>

<pre><code>[FEN ""]
[StartPly "5"]

1. e4 d5 2. exd5 Qxd5 3. c4 Qe4+ 4. Qe2 (4. Be2 Qxg2 5. Bf3 Qg6) Qxe2+ 5. Bxe2 c5
</code></pre>

<p>In the final position:</p>

<ul>
<li>White's b- and d-pawns are restrained</li>
<li>Although White has developed the bishop, it is not a good piece yet</li>
</ul>

<p>I think the evaluation is dynamic equality here.</p>
 12449: <p>This is what I try to accomplish as white, but I play Nf3 first.
Although your can't take advantage this early, there are good moves depending on your temperament.</p>

<p>Qe4+ forces Qe2, else a pawn hangs, and the trade of queens.</p>

<p>Qa5 pins the d-pawn which gives you the opportunity to get in c5 (e5 is more drawish) and get a central majority.</p>

<p>With a normal game continuation, that is Qa5 => Nf6..., the d-pawn is slightly weaker as white can't play c3 to support it.  </p>

<p>Just the opinion of a 2000 player.</p>
