reorder scripts preamble

src/GameState.gd

@@ -1,5 +1,7 @@
-extends Node
 class_name GameState
+extends Node
+
+signal state_changed(previous, new)
 
 # https://github.com/GDQuest/godot-demos/blob/master/2018/04-24-finite-state-machine/player_v2/state_machine.gd
 # http://www.gameprogrammingpatterns.com/state.html
@@ -11,8 +13,6 @@ var transitions = {
 	State.GAME_OVER : [ State.MAIN ]
 }
 
-signal state_changed(previous, current)
-
 export(State) var current_state = State.MAIN
 
 func current_state_name() -> String:

src/Piece.gd

@@ -1,6 +1,6 @@
 tool
-extends Node2D
 class_name Piece
+extends Node2D
 
 export var size: int = 160
 

src/Taquin.gd

@@ -1,6 +1,6 @@
 tool
-extends Control
 class_name Taquin
+extends Control
 
 var Piece = preload("res://src/Piece.tscn")