Message board topic:

Hey John, so talking out many senerios with the AI I decided to tweak chess and came up with a new version (laugh). Here are the basic rules. What do you think of it? I am still trying to decide if it would be good or not and it is possible the game is normal if no one promotes a pawn to the new piece. I MAY ask the AI to play me once, but high chance it is a standard game only.

 

Royal Succession Chess
(Standard Chess + Optional Prince Promotion & King Respawn)The Board & Pieces
Same 8x8 board, same starting position as regular chess.
All normal pieces (King, Queen, Rook, Bishop, Knight, Pawn) move and capture exactly as in standard chess.
New optional piece: the Prince (see below).
Pawn Promotion
When a pawn reaches the 8th rank (or 1st rank for Black), it must promote.
You may choose:

Queen, Rook, Bishop, or Knight (as in standard chess), OR
Prince (new piece).
You may have up to 8 Princes (one per pawn that chooses this path).

Prince Movement & Capture
Moves exactly 1 square in any direction (horizontal, vertical, or diagonal).
Captures any enemy piece on an adjacent square (including protected pieces).
Cannot jump over pieces.
Not royal: capturing a Prince does not end the game.

Think of it as a "baby king" that walks one step at a time but can bite anything next to it.King Succession (Optional Rule - Only Active if You Promote to Prince)
There is always exactly one king on your side.
If your current king is captured AND you have at least one Prince:

The oldest living Prince (the one promoted first) instantly transforms into your new king.
If you have no Prince when your king is taken -> you lose (checkmate, same as standard chess).
The new king keeps the same turn order; the opponent does not get an extra move.

Important: If you never promote to Prince, this rule never triggers. Game plays exactly like normal chess.Check, Checkmate & Stalemate
Check: The current king is attacked and must escape.
Checkmate: The current king has no legal move to escape capture -> you lose.
Stalemate: The current king has no legal moves but is not in check -> draw.
Princes do not cause or avoid stalemate on their own.
Winning the Game
You win by:
Checkmating your opponent's current king (with or without their Princes to save them), OR
Your opponent resigns.
Draw Rules (Same as Standard Chess)

Stalemate
Threefold repetition
50-move rule (no capture or pawn move)
Insufficient material (e.g., K vs. K, K+P vs. K with blocked pawn, etc.)
Agreement

Note: K + Prince vs. K is a win; the Prince helps force mate.Notation & Symbols
Prince symbol: Use P (uppercase) or a custom icon.
Promotion: e8=P -> Prince; e8=Q -> Queen (as usual).
King respawn: Note in commentary: (King captured, oldest Prince -> new King)
Example Mini-Game
e4 e5
Qh5 Nc6
Bc4 Nf6??
Qxf7# -> King captured!
-> If Black had promoted a pawn to Prince earlier, it becomes the new king and play continues.
-> If not, Black loses (standard checkmate).

Summary BoxROYAL SUCCESSION CHESS
Pawn promotion: Queen/Rook/Bishop/Knight OR Prince (1-step any direction, captures anything adjacent)
King taken? -> Oldest Prince becomes new King (only if you have one)!
No Prince? -> Normal checkmate.
Mix and match: Go full Queen swarm or build a royal dynasty.
All other rules = standard chess.
K + Prince vs K = WIN.

I asked the AI "explain the logic of pawn to prince promotion and that strategy and how often it may happen." and it said:

In Royal Succession Chess, promoting a pawn to a Prince instead of the usual queen, rook, bishop, or knight is a strategic choice driven by the Prince's unique abilities and the game's king succession rule. The Prince moves one square in any direction like a non-royal king and captures any adjacent enemy piece, making it a flexible defender worth about 3-4 points. Its real power is as a backup king: if your current king gets captured, the oldest Prince instantly becomes your new king, letting you survive what would be checkmate in standard chess. You can have up to 8 Princes, giving up to 8 extra lives.

The logic starts with risk-reward. A queen gives immediate firepower to attack or end the game fast, but Princes prioritize survival and long-term resilience. Key reasons to choose Prince:

First, king insurance. In aggressive openings or if your king is exposed, promote early pawns to Princes as hidden backups. You can then sacrifice your king in a bold attack, respawn elsewhere, and continue while the opponent wastes time celebrating a false win.

Second, unbeatable endgames. King plus one Prince beats a lone king, since the Prince helps trap it perfectly, unlike king plus bishop or knight which draw. In late games after queens trade, a Prince turns draws into wins.

Third, top-tier defense. Princes guard eight squares around them, shield your king, capture threats up close, and form fortresses. Cluster a few around your king for an ironclad setup.

Fourth, avoids mistakes like stalemate. A queen might overcontrol the board and stalemate a trapped enemy king; a Prince is subtler and keeps options open.

Fifth, cheap aggression. Princes are low-value so you can sac them for tempo, forks, or promotion checks without big loss, especially since capturing one does not end the game.

The strategy fits defensive or comeback play. Early game, promote 1-2 edge pawns to Princes for insurance while queening central ones for offense. Midgame, if down material or kings are unsafe, rush more Princes. Endgame, they shine in minor piece battles. Mix them: queens for attack, Princes for dynasty-building. Opponents must hunt multiple kings, buying you counterplay time.

How often? Rare in most games, like 1-5 percent of promotions, since queens win quicker. Expect it situationally: 20-30 percent in defensive setups, defensive player styles, or when racing pawn promotions. In casual or bullet games, more frequent for fun; in serious play, only when insurance or endgame edge matters. Like standard chess underpromotions to knight at under 2 percent, Prince promo adds fresh tactics without dominating.

Wow, you put a ton of thought into this!  I'd heard proposals for an extra piece, though nothing specific, and nothing about promoting to a piece that didn't exist before.  Of course, there are some variations now.  Fischer Random, (also known as freestyle), Crazy House, 360 and probably more.  I really don't like the Fischer Random idea for myself.

Ben Finegold, (a popular chess streamer) said that most of us have enough trouble with standard chess.  I learned the rules to 3D chess but decided pretty quick I needed to master 2D chess first, and I don't think that'll ever happen.

Will AI be up for playing this new version with you?  Sounds like it has a grasp of the concept.  I can't imagine how much trouble I'd have with the Prince concept.  John