Add difficulty-based reference image and ghost slot visibility to Jigsaw

- Hide the faint full-picture reference on Hard and Legendary levels
- Show the target-slot ghost preview only on Easy while dragging a piece
- Store the selected difficulty on the scene for these checks

src/games/jigsaw/JigsawGame.js

@@ -372,6 +372,7 @@ export default class JigsawGame extends Phaser.Scene {
     this.startTime = 0; this.elapsed = 0;
     this.seed = (Math.random() * 1e9) | 0;
     this.jig = makeJigsaw(this.cols, this.rows, this.seed);
+    this.difficulty = this.selectedDiff;
     this.diffLabel = `${cfg.label} · ${this.total} pieces`;
     this.imageName = item.name || 'Image';
 
@@ -402,6 +403,8 @@ export default class JigsawGame extends Phaser.Scene {
     if (this.textures.exists('jigsaw-ref')) this.textures.remove('jigsaw-ref');
     this.textures.addCanvas('jigsaw-ref', rcv);
     this.refImage = this.add.image(bcx, bcy, 'jigsaw-ref').setDisplaySize(BOARD.size, BOARD.size).setAlpha(0.16).setDepth(3);
+    // Faint full-picture reference: keep on Easy/Medium, hide on Hard/Legendary.
+    this.refImage.setVisible(this.difficulty !== 'hard' && this.difficulty !== 'legendary');
 
     // Build piece textures + sprites
     const texKey = (r, c) => `jg-${this.seed}-${r}-${c}`;
@@ -636,7 +639,12 @@ export default class JigsawGame extends Phaser.Scene {
     piece.img.setDepth(this.zTop);
     this.dragging = { piece, offX: piece.img.x - w.x, offY: piece.img.y - w.y };
     this.suppressNextButtonClick = true;
-    this.ghost.setTexture(piece.img.texture.key).setPosition(piece.home.x, piece.home.y).setVisible(true);
+    // Show the target ghost (brighter alpha preview of the home slot) on Easy only.
+    if (this.ghost && this.difficulty === 'easy') {
+      this.ghost.setTexture(piece.img.texture.key).setPosition(piece.home.x, piece.home.y).setVisible(true);
+    } else if (this.ghost) {
+      this.ghost.setVisible(false);
+    }
     playSound(this, SFX.UI_PICK);
   }