Refactor function `turn` to `update_dirxy`

- More explicit name
- Push error if direction enum out of range
- Remove useless argument

Player.gd

@@ -46,7 +46,7 @@ func _ready():
 	posix = int (position.x / 64)
 	posiy = int (position.y / 64)
 
-	turn(dire)
+	update_dirxy()
 
 	tween.connect_into(self)
 
@@ -94,7 +94,7 @@ func move():
 		if dire > 3:
 			dire = 0
 
-	turn(dire)
+	update_dirxy()
 	dire_delta = 0
 
 	posix += dirx
@@ -111,17 +111,19 @@ func has_block_on_side(left_or_right:int):
 	# TODO : use enum for blocks
 	return grid.get_cell(bposx, bposy) == 1
 
-func turn(dir:int):
+func update_dirxy():
 	dirx = 0
 	diry = 0
-	if dir == Direction.UP:
+	if dire == Direction.UP:
 		diry -= 1
-	elif dir == Direction.RIGHT:
+	elif dire == Direction.RIGHT:
 		dirx += 1
-	elif dir == Direction.DOWN:
+	elif dire == Direction.DOWN:
 		diry += 1
-	else:
+	elif dire == Direction.LEFT:
 		dirx -= 1
+	else:
+		push_error("dire out of range")
 
 func die():
 	alive = false