user20509: chess.com says this move is a blunder, so it must be really bad, not simply bad. I don't understand why, and I'm out of my one free daily analysis. Could you please explain why?
I chose this move because, a) winning a pawn on a square that isn't attacked by anything seems better than losing my pawn on f4, and b) because doubled pawns on the king's file looks like good protection until I castle (if at all).
[FEN ""]
[Startply "5"]

1. e4 e5 2. f4 Bc5 3. fxe5?? {[%draw full,f4,yellow][%draw arrow,f4,e5,red]}


user28052: In general it is not good to open up the kingside wide open without developing pieces, especially since f2 and that diagonal is weak (think Fool's mate). Queen pawn moves are inherently safer since the queen is ready to back up the pawn if needed, making an aggressive Black queen pawn capture like Qxd4 impossible compared to Qxe4+.

user9064: Taking the e5 pawn allows black a devastating check on h4 with the queen, which (after blocking with pawn to g3) inevitably allows black to capture the e4 pawn with check again, winning your h1 rook.
Keeping your pawn at f4 prevents all that, given that now Qh4+ can be successfully blocked with g3. The f pawn blocks the queen's path to e4.
Furthermore, if you immediately play the knight to f3 instead of capturing e5, you eliminate the queen check threat altogether - provided you keep your knight on f3 for a while of course.

20509: <p>chess.com says this move is a blunder, so it must be <em>really</em> bad, not simply bad. I don't understand why, and I'm out of my one free daily analysis. Could you please explain why?</p>
<p>I chose this move because, a) winning a pawn on a square that isn't attacked by anything seems better than losing my pawn on f4, and b) because doubled pawns on the king's file looks like good protection until I castle (if at all).</p>
<pre><code>[FEN &quot;&quot;]
[Startply &quot;5&quot;]

1. e4 e5 2. f4 Bc5 3. fxe5?? {[%draw full,f4,yellow][%draw arrow,f4,e5,red]}
</code></pre>
 28052: <p>In general it is not good to open up the kingside wide open without developing pieces, especially since f2 and that diagonal is weak (think Fool's mate). Queen pawn moves are inherently safer since the queen is ready to back up the pawn if needed, making an aggressive Black queen pawn capture like Qxd4 impossible compared to Qxe4+.</p>
 9064: <p>Taking the e5 pawn allows black a devastating check on h4 with the queen, which (after blocking with pawn to g3) inevitably allows black to capture the e4 pawn with check again, winning your h1 rook.</p>
<p>Keeping your pawn at f4 prevents all that, given that now Qh4+ can be successfully blocked with g3. The f pawn blocks the queen's path to e4.</p>
<p>Furthermore, if you immediately play the knight to f3 instead of capturing e5, you eliminate the queen check threat altogether - provided you keep your knight on f3 for a while of course.</p>
