extracted some logic to the piece class and

implemented the knights legal moves

src/logic/pieces/knight.py

@@ -1,5 +1,16 @@
 from .piece import Piece
 
 class Knight(Piece):
-    pass
+    def legal_moves(self, board: "Board") -> list["Move"]:
+        ret = []
+        for dx, dy in [
+            (+2, +1), (+1, +2), # north east
+            (+2, -1), (+1, -2), # south east
+            (-2, -1), (-1, -2), # south west
+            (-2, +1), (-1, +2), # north west
+        ]:
+            move = self._move_for_position(board, self.pos.x + dx, self.pos.y + dy)
+            if move is not None:
+                ret.append(move)
+        return ret