Noth players mark down their moves and act at the same time.
What happens if both players want to move to the same square? Or the double move leaves one (or even both) players in check?
Okay, so what happens when you’re playing with someone who doesn’t notice he/she is in check? You let them move, then go “No, no, no, no, no! Can’t do that. You’re in check, Bucko!”?
I actually like en passant. If I had to change a rule, it would be a restriction on promotions - once you promote a pawn to a specific piece, you cannot promote another pawn to the same one until the first promoted piece is gone. Maybe permit seconds if a player has promoted one of each already - but how often does that happen?
I’d change the rule requiring that effeminate droids must always let wookies win. Seems racist.
Oh, OK.
I was confused because RikWriter seemed to think you had to announce check.
I was thinking rankings. Queen beats bishops beats knight beats rook etc.
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Or the double move leaves one (or even both) players in check?
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Then both are in check and must move their king to leave it.
If it ain’t broke, don’t make an omelette out of it! 
I estimate I get an en passant capture in about 1-2% of my games.
It would matter most in endings, funnily enough.
Suppose Black had a couple of pawns on a7 and b6. During the middle game I play b5, fixing both pawns. In the resulting King and pawn ending, I have effectively a pawn advantage due to en passant. If Black can play a7-a5 without being captured, my strategy from the middle-game fails.
So the only answer to e4 is e6? Yup, it’s a ‘single path’ game all right!
Well, yes.
In a tournament, you simply point at the offending king, they blush :o and retract their move. (Of course ‘touch move’ is still in effect.)
If training or playing a beginner, you break it gently. 
“Sorry, you’re in check.”
So under your rule:
- even if I have my original queen, I can promote a pawn to another queen
- but I can’t have another queen promotion until my previously promoted queen is captured?
I did have a serious game where I got two pawns to the 7th rank by move 25 (my original queen was still present!), and duly promoted one. Sadly my opponent resigned before I could promote a second time.
Apart from that, I have never had a second promotion in thousands of tournament games…
I run tournaments where before the tournaments, the organizers of the tournament made up some new rule, or new piece, or something. Then people would show up, all be told the new rule at the same time, and play.
After the tournament, no one would ever use that rule/piece again, unless it turned out to be one that people particularly liked.
Of course, my favorite game is Magic: The Gathering…
Each player gets to secretly designate a single piece (not the king) as nuclear. The piece can capture other pieces normally, but if it is captured, the entire board is considered vaporized and the game is a draw.
I’m not a very good chess player, so I’d be putting the designation on one of my opponent’s pawns…a LOT.
Of course, this rule goes out of effect unless you pronounce it nuh-cuh-leh-ahr.
En passant is a pretty silly rule… But lack of en passant is actually even sillier. The situation seldom comes up, precisely because of the en passant rule, but without it, a pawn could slip past the enemy pawns which would otherwise threaten to capture it by making its two-space initial move.
Myself, I’ve never liked the rule that the game ends in checkmate. It seems to reflect an antiquated notion about the propriety of kings on a battlefield. I say, just capture the king like any other piece. Of course, your opponent will never let you do so, so long as he has any other option, so the actual gameplay would remain unchanged (at least in regular chess). But I like the flavor more, and it does actually make a difference in many chess variants. For instance, in many-player variants, you might choose to end your turn in check, and hope that one of your other opponents will take care of it for you.
There’s a very good reason for it: it ensures that opposing pawns in adjacent files can’t pass each other without a chance to be captured.
I’m not sure, but my theory is that the rule that lets you move a pawn two spaces was added at some point, to save time in the opening when players often have pawns in opposition at the 4th and 5th rank in the king’s, queen’s or queen’s-bishop file. In order to not change the dynamics of the game, they simultaneously (or soon after) added the en-passant rule.
That’s exactly right. Anybody who thinks en passant is a frivolous or disposable rule doesn’t understand chess.
That’s not to say that the rule couldn’t be eliminated–the purpose of the thread, after all, is to discuss changes–but arguing for its elimination on the ground that it’s an illogical technicality is wrong.
Personally, I’d like to eliminate white’s advantage by making the game a draw if each player captures the opposing king on the same move. When white puts black in check, black would have the same three options as today (move the king, interpose, or capture) plus a fourth option of putting white in check. White could then either accept a draw by capturing black’s king (forcing black to counter-capture white’s king), or white could respond to black’s check.
Introduce the drop rule, as used in Shogi (Japanese chess). Captured pieces, instead of being removed from the game permanently, become the property of the capturing player. At any time, instead of making a move, you can replace a previously captured piece on the board as your own. (You’d need an extra set handy, since this requires the piece to change from black to white or vice versa.)
A friend and I (the friend went on to become an international master) once invented Toroidal Chess, a variation of cylindrical chess. Not only are the two sides of the board joined (so you can move off the left and onto the right), but so are the two ends of the board. Thus, the board is effectively a doughnut shape, or torus.
Since on a regular board this would mean that the two players’ pieces are adjacent to each other, meaning instant all-out war, the game is instead played on a 14x8 board, where each player has two rows of pawns, one on each side of their pieces.
I think we also had to make a rule that pieces couldn’t move more than eight squares, or a bishop’s move (for example) could cover virtually the whole board, if there were no blocking pieces.
Made for an interesting game.
This is a variant I invented and have actually played. When you have one of your rooks immediately in front of one of your pawns, you may move the pawn forward and place it on top of the rook. On your next turn (if the rook-pawn has not been captured) you may send the pawn flying in any direction by flicking it with your finger. The pawn and any pieces it knocks down (of either color) are considered captured. If a king is knocked over, that player loses; if both kings are felled, it’s a draw.