Reset DepthStencilState to None before Skybox.Draw

Celeste.Mod.mm/Patches/Skybox.cs

@@ -0,0 +1,26 @@
+#pragma warning disable CS0626 // Method, operator, or accessor is marked external and has no attributes on it
+#pragma warning disable CS0108 // Member hides inherited member; missing new keyword
+
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using Monocle;
+using MonoMod;
+
+namespace Celeste {
+    class patch_Skybox : Skybox {
+
+        public patch_Skybox(VirtualTexture texture, float size = 25) 
+            : base(texture, size) {
+        }
+
+        public extern void orig_Draw(Matrix matrix, Color color);
+
+        public void Draw(Matrix matrix, Color color) {
+            // the orig method doesn't reset DepthStencilState to None.
+            // Some mods may begin a new SpriteBatch with DepthStencilState set to Default,
+            // which causes the Skybox to be rendered in front of the mountain.
+            Engine.Graphics.GraphicsDevice.DepthStencilState = DepthStencilState.None;
+            orig_Draw(matrix, color);
+        }
+    }
+}