A lot of UI work....

opening slash animation
main menu
load first level

Scripts/Main.cs

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+using Godot;
+using Godot.Collections;
+
+public partial class Main : Node
+{
+   [Export]
+   public Array<PackedScene> Levels;
+}

Scripts/MainMenu.cs

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+using Godot;
+using System.Linq;
+
+public partial class MainMenu : Node2D
+{
+   private AnimationPlayer _player;
+
+   [Signal]
+   public delegate void IntroAnimationsCompletedEventHandler();
+
+   public override void _Ready()
+   {
+      GetParent().GetNode<TextureRect>("MainMenu/UIAnimations/LoreSplash").Show();
+      _player = GetTree().Root.GetNode<AnimationPlayer>("/root/Main/MainMenu/UIAnimations/AnimationPlayer");
+      _player.Queue("IntroLore");
+   }
+
+   private void OnStartButtonPressed()
+   {
+      _player.Play("FirstLevel");
+      Hide();
+      _player.AnimationFinished += OnAnimationFinished;
+   }
+
+   private void OnAnimationFinished(StringName animationName)
+   {
+      if (animationName == "FirstLevel")
+      {
+         var main = GetTree().Root.GetNode<Main>("Main");
+         var firstLevel = main.Levels.First().Instantiate();
+         AddChild(firstLevel);
+      }
+   }
+}