initial stab at disk 3 area.

Also made hidden items visible by default since they will become hidden when the game starts anyway. This way they are visible in the editor.

hidden_coin.tscn

@@ -8,7 +8,7 @@
 [sub_resource type="CapsuleShape2D" id="CapsuleShape2D_6qpsl"]
 height = 26.0
 
-[node name="HiddenCoin" type="Node2D" unique_id=1739014101]
+[node name="HiddenCoin" type="Node2D" unique_id=1739014101 groups=["Hidden"]]
 visible = false
 script = ExtResource("1_4tl78")