Interesting. Hmmm, I have to think this through. I believe that if the game followed normal chess rules, except for replacing the pieces with queens, then games where the captures are all even trades would result in draws, but if one side could come out ahead with K+Q vs K, then there would be the usual mate sequence.

HOWEVER the rule OP added that "a piece may only move if it is adjacent to another piece of either color" slightly complicates the endgame. My normal tendency would be to put the queen far away from the action to avoid blundering it, but here that would instantly deactivate it. It's kind of funny to picture the kings racing across the board to capture or reactivate the last inert queen.

I think one can still get the usual style of mate in this variant, you just have to walk the king and queen together, and pay extra attention to avoiding stalemate. For example, imagining white king on e1, black king on e3, black queen on d3. If white to move then Qb1# or Qe2#, fairly standard maneuvers (though if black to move that's a stalemate).

This is an interesting modification to the game, I'd play a few rounds...

My guess/intuition is that the first player to move can win. I see two strategies that may work:

- use your queens ‘from the outside in’ to give check, forcing your opponent to take the queen giving check. In the long run, isolate an enemy queen in a corner, effectively removing it from play and giving you a surplus queen. Then, keep exchanging queens.

- use your queens to give check, forcing the queens near the enemy king to take them. Once the enemy king is isolated, it cannot move anymore, so giving check becomes dangerous. Black will have to either take the queen giving check or move a queen into the line of sight.