Setup UI canvas, added shield and game start.

player.gd

@@ -1,6 +1,12 @@
 extends Area2D
 
+signal died
+signal shield_changed
+
 @onready var screensize = get_viewport_rect().size
+@export var max_shield = 10
+var shield = max_shield:
+    set = set_shield
 @export var speed = 150
 @export var cooldown = 0.25
 @export var bullet_scene : PackedScene
@@ -10,9 +16,17 @@ func _ready():
     start()
 
 func start():
+    shield = max_shield
     position = Vector2(screensize.x / 2, screensize.y - 64)
     $GunCooldown.wait_time = cooldown
 
+func set_shield(value):
+    shield = min(max_shield, value)
+    shield_changed.emit(max_shield, shield)
+    if shield <= 0:
+        hide()
+        died.emit()
+
 func shoot():
     if not can_shoot:
         return
@@ -41,6 +55,10 @@ func _process(delta):
 func _on_gun_cooldown_timeout():
             can_shoot = true
 
-
 func _on_gun_cool_down_timeout() -> void:
   can_shoot = true
+
+func _on_area_entered(area):
+    if area.is_in_group("enemies"):
+        area.explode()
+        shield -= max_shield / 2