getting pretty close actually :)

Camera2D.gd

@@ -1,17 +1,39 @@
 extends Node
 
+export (PackedScene) var Tower = preload("res://Tower.tscn");
+
 onready var screen_size = Vector2(ProjectSettings.get("display/window/size/width"), ProjectSettings.get("display/window/size/height"))
 onready var player = get_node("Player")
 
+export var tower_density = 200
+var last_built = 100
+
+func build_tower():
+	var tower = Tower.instance()
+	tower.connect("exit", self, "_on_Tower_exit")
+	var pos = Vector2(last_built, randf() * screen_size.y - screen_size.y / 2)  # The player's movement vector.
+	tower.position = pos
+	
+	add_child(tower)
+	last_built += tower_density
+
 func update_view():
 	var canvas_transform = get_viewport().get_canvas_transform()
 	var pos = player.position
 	pos.y = 0
-	canvas_transform[2] = -player.position + screen_size / 2
+	canvas_transform[2] = -pos + screen_size / 2
 	get_viewport().set_canvas_transform(canvas_transform)
 
 func _ready():
+	randomize()
 	update_view()
 	
+	print(screen_size)
+	while last_built < screen_size.x * 2:
+		build_tower()
+	
 func _on_Player_move():
 	update_view()
+
+func _on_Tower_exit():
+	build_tower()

Main.tscn

@@ -1,10 +1,8 @@
-[gd_scene load_steps=6 format=2]
+[gd_scene load_steps=4 format=2]
 
 [ext_resource path="res://Camera2D.gd" type="Script" id=1]
 [ext_resource path="res://icon.png" type="Texture" id=2]
-[ext_resource path="res://Tower.tscn" type="PackedScene" id=3]
-[ext_resource path="res://Tower.gd" type="Script" id=4]
-[ext_resource path="res://Player.tscn" type="PackedScene" id=5]
+[ext_resource path="res://Player.tscn" type="PackedScene" id=3]
 
 [node name="View" type="Node"]
 script = ExtResource( 1 )
@@ -18,14 +16,8 @@ texture = ExtResource( 2 )
 expand = true
 stretch_mode = 2
 
-[node name="Tower" parent="." instance=ExtResource( 3 )]
-position = Vector2( 734.801, 66.482 )
-gravity_scale = 0.0
-script = ExtResource( 4 )
-
-[node name="Player" parent="." instance=ExtResource( 5 )]
-position = Vector2( 571.569, 183.117 )
+[node name="Player" parent="." instance=ExtResource( 3 )]
+position = Vector2( 136.52, -24.4934 )
 gravity = 0.0
 collision_layer = 0
-[connection signal="body_entered" from="Tower" to="Tower" method="_on_Tower_body_entered"]
 [connection signal="move" from="Player" to="." method="_on_Player_move"]

Player.gd

@@ -32,6 +32,6 @@ func _process(delta):
 
 func _on_Player_body_entered(body):
 	print("HIT")
-	hide()  # Player disappears after being hit.
+	#hide()  # Player disappears after being hit.
 	emit_signal("hit")
 	$CollisionShape2D.set_deferred("disabled", true)

Tower.gd

@@ -1,5 +1,6 @@
-extends RigidBody2D
+ extends Node2D
 
+signal exit
 # Declare member variables here. Examples:
 # var a = 2
 # var b = "text"
@@ -15,3 +16,8 @@ func _ready():
 func _on_Tower_body_entered(body):
 	print("HIT HERE")
 	pass # Replace with function body.
+	
+func _on_Visibility_screen_exited():
+	print("Leaving")
+	queue_free()
+	emit_signal("exit")

Tower.tscn

@@ -1,23 +1,40 @@
-[gd_scene load_steps=3 format=2]
+[gd_scene load_steps=4 format=2]
 
-[ext_resource path="res://icon.png" type="Texture" id=1]
+[ext_resource path="res://Tower.gd" type="Script" id=1]
+[ext_resource path="res://icon.png" type="Texture" id=2]
 
 [sub_resource type="RectangleShape2D" id=1]
 extents = Vector2( 29.9672, 132.942 )
 
-[node name="Tower" type="RigidBody2D"]
-position = Vector2( -32, 50 )
-collision_mask = 0
-__meta__ = {
-"_edit_group_": true
-}
+[node name="Tower" type="Node2D"]
+script = ExtResource( 1 )
 
-[node name="TextureRect" type="TextureRect" parent="."]
+[node name="Lower" type="RigidBody2D" parent="."]
+position = Vector2( -32, 100 )
+
+[node name="TextureRect" type="TextureRect" parent="Lower"]
 margin_right = 64.0
 margin_bottom = 256.0
-texture = ExtResource( 1 )
+texture = ExtResource( 2 )
 expand = true
 
-[node name="CollisionShape2D" type="CollisionShape2D" parent="."]
+[node name="CollisionShape2D" type="CollisionShape2D" parent="Lower"]
 position = Vector2( 31.5038, 135.281 )
 shape = SubResource( 1 )
+
+[node name="Upper" type="RigidBody2D" parent="."]
+position = Vector2( 32, -100 )
+rotation = 3.14159
+
+[node name="TextureRect" type="TextureRect" parent="Upper"]
+margin_right = 64.0
+margin_bottom = 256.0
+texture = ExtResource( 2 )
+expand = true
+
+[node name="CollisionShape2D" type="CollisionShape2D" parent="Upper"]
+position = Vector2( 31.5038, 135.281 )
+shape = SubResource( 1 )
+
+[node name="VisibilityNotifier2D" type="VisibilityNotifier2D" parent="."]
+[connection signal="screen_exited" from="VisibilityNotifier2D" to="." method="_on_Visibility_screen_exited"]

project.godot

@@ -24,6 +24,11 @@ config/icon="res://icon.png"
 window/size/width=420
 window/size/height=640
 
+[physics]
+
+2d/default_gravity=0
+2d/default_gravity_vector=Vector2( 0, 0 )
+
 [rendering]
 
 quality/driver/driver_name="GLES2"