Shadow - a new game idea on a chess board

Hi Everyone. I am totally new to this kind of board game design thing, but I happen to have an idea for a new game (surprise). It all started because I was getting tired of losing to my brother in chess, so I decided to make a new game that I would have better chances at!
I tried to be very detailed in the rules (sorry they’re so long!) so that if you want you can effectively playtest this game. Here they are:
Shadow - rules and gameplay (2 players)

My game is called Shadow. It is played on a chess board, excluding all of the squares on the perimeter, meaning that it is a 6x6 board. There are four main pieces. Both players have a King piece and a Shadow piece. I actually whittled some special pieces for the King and the shadow, but if you want to playtest using chess pieces, using a king as the King and a bishop as the Shadow would work (you want the shadow to be a smaller piece). As in chess, there is a black and a white team. The King and the Shadow are placed on the middle two squares on their side of the board, it’s up to you which is on the left or right. Black goes first since it’s the color of a shadow :) (and since night comes before day).

Movement: Each piece can move one space in any direction, including diagonally. However, the shadow piece must be in one of the eight spaces adjacent to the King at all times. In a turn, a player moves his King first, and then his shadow. In this way, the Shadow piece tends to trail the King, like a real shadow. This also prevents a player from ever moving their King into the space where their Shadow just was. A player can also choose to move only their King, as long as the Shadow remains in an adjacent space. A player can never only move their Shadow.

Objective 1 - 1st way to win: One of the main objectives is to capture the opponent’s shadow with your King by landing on it. Kings are the only pieces that can capture, and they only can capture the opponent’s shadow. This means no King capturing another King, no Shadow capturing another Shadow, and no Shadow capturing a King.

Striking Distance: When a player’s King is one move away from the opponent’s Shadow, this is called Striking Distance, or SD.

SD Blocks: When a player moves into SD, they are allowed to place an SD block piece of their color to place on that same turn. (if playtesting with chess pieces, use pawns as blocks or maybe checkers). These are drawn from piles, (one pile for each color).The player can place the block in two kinds of places. #1: in a space. This means that no King can now move into that space. #2: on an intersection. This means that diagonal movement between any of the four spaces that the block is touching is prohibited for Kings. The outer intersections are fair game for placing blocks. Notice, I only mentioned the Kings. Shadows have different relationships with blocks (explained later).
Important Note: A player can move into SD two times in a row and place an SD block. On the third time that they move into SD in a row, they are no longer able to place another SD block. They must move out of SD to break the chain of turns in SD. After that they can move back into SD if desired and again get an SD block two times in a row.
This means that a player cannot continually dominate play by moving into SD and placing blocks over and over. There is more of a back and forth between players. Also a player may never place a block that completely separates the two Kings
Also.. During the game, if it is a player’s turn and they cannot move or do any action, then it is a stalemate

Objective 2: 2nd way to win: By placing 4 blocks in a row of their color on the board. These can be vertical, horizontal, or diagonal. They can be all on spaces, all on intersections, or in the case of diagonals only, they could also be alternating between spaces and intersections.

Personal Blocks (P Blocks): As mentioned before, Shadows have a different relationship with blocks. They can interact more with them, unlike the Kings. A shadow can move diagonally over a block that is on an intersection. The Shadow is still only moving one space, but it hops the block. This block that has been hopped is removed from the board, regardless of the color, and the player who hopped it is given a Personal Block of their color. This P block goes off the board in a personal stash of that player. To play a P block, a whole turn is required just to play the block. So you cannot get a P block and play it on the same turn. This brings us to…

Objective 3: 3rd way to win: By having 3 P blocks in your stash at one time.

There are two other ways of obtaining a P block.
#1: landing on a block that is in a space, regardless of color. The player must commit to this move, since the Shadow has to sit on this block for 1 extra turn before it can be moved off and the block removed and turned into a P block of their color. So, the Shadow lands on the block. The next turn the King has to move, and then the turn after that the Shadow can move off and the block can be removed. NO landing on a block and moving off the next turn!
#2: capturing two of the opponent’s blocks by putting your colored blocks on either end. This forms a line with all four blocks that has no inconsistent gaps. The two middle blocks are removed and turn into P blocks for the capturer.
Important note: The capturer has to be the last one to play the end block to make an eligible capture. A person cannot fall into a capture by filling in one of the middle spaces and completing the capture. This is how captures in the game Pente Work.

Hopefully this all makes sense. Please ask if you have any rule questions. I would love for people to playtest this using chess pieces and checkers, and then giving me feedback. It would be REALLY appreciated. I hope you all enjoy learning and playing this new game. Remember, there are 3 ways to win, so you have options!
Thanks,
Martin S