yes

Sources/Engine/Pieces/King.swift

@@ -1,6 +1,19 @@
 final class King: Piece {
 	typealias Threats = (Piece?, Piece?)
-	var threats: Threats = (nil, nil)
+	internal private(set) var threats: Threats = (nil, nil)
+
+	func insertThreat(_ piece: Piece) {
+		if threats.0 == nil {
+			threats.0 = piece
+			return
+		}
+
+		if threats.1 == nil {
+			threats.1 = piece
+			return
+		}
+	}
+
 	override var unicodeRepresentation: String {
 		return color == .Black ? "♚" : "♔"
 	}