Setup UI canvas, added shield and game start.

main.gd

@@ -1,9 +1,18 @@
 extends Node2D
 
+@onready var start_button = $CanvasLayer/CenterContainer/Start
+
 var enemy = preload("res://enemy.tscn")
 var score = 0
 
 func _ready():
+    start_button.show()
+#   spawn_enemies()
+
+func new_game():
+    score = 0
+    $CanvasLayer/UI.update_score(score)
+    $Player.start()
     spawn_enemies()
 
 func spawn_enemies():
@@ -17,3 +26,9 @@ func spawn_enemies():
 
 func _on_enemy_died(value):
     score += value
+    $CanvasLayer/UI.update_score(score)
+
+
+func _on_start_pressed():
+    start_button.hide()
+    new_game()