Add HUD scene with elevator hack timing minigame

- elevator panel w/ a screen and close button
- screen.gd timing minigame: sweep line bounces across a shrinking target zone
- hud wiring to move down floors on successful hacks, countdown/win states, and speed up AI on misses

hud.gd

@@ -0,0 +1,41 @@
+extends Control
+
+# I HAVE NO IDEA WHAT I'M DOIN!!!
+var current_floor := 10
+var saved_count := 0
+
+var doors_closing := false
+
+
+func _ready():
+	$ElevatorPanel/PanelMargin/PanelColumn/CloseButton.pressed.connect(_on_close_pressed)
+	# 10 floors is probably a lot but will make testing easier.
+	$StatsMargin/StatsColumn/FloorLabel.text = "FLOOR: 10"
+
+func _unhandled_input(event):
+	if event is InputEventKey and event.pressed and event.keycode == KEY_SPACE:
+		_on_close_pressed()
+
+func _on_close_pressed():
+	# don't let 'em spam the button
+	if doors_closing:
+		return
+	var screen = $ElevatorPanel/PanelMargin/PanelColumn/Screen
+	var success = screen.attempt_hack()
+	if success:
+		doors_closing = true
+		saved_count += 1
+		current_floor -= 1
+		$StatsMargin/StatsColumn/SavedLabel.text = "SAVED: " + str(saved_count)
+		$StatsMargin/StatsColumn/FloorLabel.text = "FLOOR: " + str(current_floor)
+		if current_floor <= 1:
+			screen.show_win()
+		else:
+			screen.show_countdown()
+			var tween = create_tween()
+			tween.tween_callback(func():
+				screen.reset_hack()
+				doors_closing = false
+			).set_delay(2.0)
+	else:
+		print("MISSED! AI is faster now!")