it is done

core/src/mindustry/ui/fragments/FadeInFragment.java

@@ -0,0 +1,39 @@
+package mindustry.ui.fragments;
+
+import arc.*;
+import arc.graphics.g2d.*;
+import arc.math.*;
+import arc.scene.*;
+import arc.scene.event.*;
+
+/** Fades in a black overlay.*/
+public class FadeInFragment extends Fragment{
+    private static final float duration = 40f;
+    float time = 0f;
+
+    @Override
+    public void build(Group parent){
+        parent.addChild(new Element(){
+            {
+                setFillParent(true);
+                touchable(Touchable.disabled);
+            }
+
+             @Override
+             public void draw(){
+                Draw.color(0f, 0f, 0f, Mathf.clamp(1f - time));
+                Fill.crect(0, 0, Core.graphics.getWidth(), Core.graphics.getHeight());
+                Draw.color();
+             }
+
+            @Override
+            public void act(float delta){
+                super.act(delta);
+                time += 1f / duration;
+                if(time > 1){
+                    remove();
+                }
+            }
+        });
+    }
+}