Simultaneous Chess

We all know that a player who makes the first move had an advantage but what if each player can move at the same turn? So this is Simultaneous Chess. In this variant, each player can move at the same turn. These are the rules of the game.

1. Each player will write his move.

2. They will show their move.

3. The moves will resolve.

How the moves will resolve.

1. If the moves are legal, the moves will resolve.

2. If both moves are not legal, they repeat step no. 1 and 2. but with another move.

3. If a player move is not legal, the other player will make another move.

There are many ways the game will resolve.

1. If each players pieces moves in the same square, both of their pieces are captured.

2. If each players pieces swap places, both of their pieces are captured.

3. If the pieces moves legally but not in cases 1 and 2, they occupy those squares.

En passant

If a player makes an en passant move but the other player move his piece on the square the pawn making en passant will go, the pawn that will be captured, the piece the other player move and the pawn making en passant are captured.

King in Check

If a player makes a move but the other player makes a move that will put his king in check, the player that is in check will make another move that will not put the king in check.

If both players are in check after making a move, they repeat steps 1 and 2 but with another move.

https://www.chessvariants.com/rules/simultaneous-chess

Yep they have the same name but they have different rules.