First pass. Needs testing.

Shogi.Domain/ValueObjects/ShogiBoard.cs

@@ -1,5 +1,4 @@
 using Shogi.Domain.YetToBeAssimilatedIntoDDD;
-using System.Threading.Tasks;
 namespace Shogi.Domain.ValueObjects;
 
 /// <summary>
@@ -173,9 +172,8 @@ public sealed class ShogiBoard
 	}
 
 
-	private async Task<GameOverResult> EvaluateGameOver()
+	private GameOverResult EvaluateGameOver()
 	{
-
 		if (!BoardState.InCheck.HasValue)
 		{
 			return GameOverResult.GameIsNotOver;
@@ -198,43 +196,20 @@ public sealed class ShogiBoard
 				var simState = new BoardState(BoardState);
 				simState.Move(notation, Notation.ToBoardNotation(move), false);
 				var inCheckResult = IsEitherPlayerInCheck(simState);
-				if (inCheckResult == InCheckResult.)
+				var isStillInCheck = BoardState.InCheck == WhichPlayer.Player1
+					? inCheckResult.HasFlag(InCheckResult.Player1InCheck)
+					: inCheckResult.HasFlag(InCheckResult.Player2InCheck);
+
+				if (!isStillInCheck)
+				{
+					return GameOverResult.GameIsNotOver;
+				}
 			}
 		}
 
-		// while (tasks.Any()) var result = Task.WhenAny(tasks); // Then check for GameIsNotOver and maybe return early.
-
-
-		var gameOverResult = BoardState.State
-					.Where(kvp => kvp.Value != null)
-					.Cast<KeyValuePair<string, Piece>>()
-					.Aggregate(GameOverResult.GameIsNotOver, (inCheckResult, kvp) =>
-					{
-						var newInCheckResult = inCheckResult;
-						var threatPiece = kvp.Value;
-						var opposingKingPosition = Notation.FromBoardNotation(kingInCheck.Single(king => king.Value.Owner != threatPiece.Owner).Key);
-						var positionsThreatened = threatPiece.GetPathFromStartToEnd(Notation.FromBoardNotation(kvp.Key), opposingKingPosition);
-
-						foreach (var position in positionsThreatened)
-						{
-							// No piece at this position, so pathing is unobstructed. Continue pathing.
-							if (simState[position] == null) continue;
-
-							var threatenedPiece = simState[position]!;
-							if (threatenedPiece.WhichPiece == WhichPiece.King && threatenedPiece.Owner != threatPiece.Owner)
-							{
-								newInCheckResult |= threatenedPiece.Owner == WhichPlayer.Player1 ? InCheckResult.Player1InCheck : InCheckResult.Player2InCheck;
-							}
-							else
-							{
-								break;
-							}
-						}
-
-						return newInCheckResult;
-					});
-
-		return GameOverResult.GameIsNotOver;
+		return BoardState.InCheck == WhichPlayer.Player1
+			? GameOverResult.Player2Wins
+			: GameOverResult.Player1Wins;
 
 		Vector2[] GetPossiblePositionsForPiece(Vector2 piecePosition, Piece piece)
 		{

Shogi.Domain/YetToBeAssimilatedIntoDDD/Pathing/Path.cs

@@ -1,5 +1,4 @@
 using System.Diagnostics;
-using static Shogi.Domain.YetToBeAssimilatedIntoDDD.Pathing.Path;
 
 namespace Shogi.Domain.YetToBeAssimilatedIntoDDD.Pathing;
 
@@ -20,4 +19,6 @@ public record Path
 		Step = step;
 		this.Distance = distance;
 	}
+
 	public Path Invert() => new(Vector2.Negate(Step), Distance);
+}