Refactor catch playfield size adjustment logic w.r.t. catcher position

osu.Game.Rulesets.Catch/UI/CatchPlayfieldAdjustmentContainer.cs

@@ -43,18 +43,28 @@ public CatchPlayfieldAdjustmentContainer()
         /// </summary>
         private partial class ScalingContainer : Container
         {
+            public ScalingContainer()
+            {
+                Anchor = Anchor.BottomCentre;
+                Origin = Anchor.BottomCentre;
+            }
+
             protected override void Update()
             {
                 base.Update();
 
-                // in stable, fruit fall vertically from -100 to 340.
-                // to emulate this, we want to make our playfield 440 gameplay pixels high.
-                // we then offset it -100 vertically in the position set below.
-                const float stable_v_offset_ratio = 440 / 384f;
+                // in stable, fruit fall vertically from 100 pixels above the playfield top down to the catcher's Y position (i.e. -100 to 340),
+                // see: https://github.com/peppy/osu-stable-reference/blob/1531237b63392e82c003c712faa028406073aa8f/osu!/GameplayElements/HitObjects/Fruits/HitCircleFruits.cs#L65
+                // we already have the playfield positioned similar to stable (see CatchPlayfieldAdjustmentContainer constructor),
+                // so we only need to increase this container's height 100 pixels above the playfield, and offset it to have the bottom at 340 rather than 384.
+                const float stable_fruit_start_position = -100;
+                const float stable_catcher_y_position = 340;
+                const float playfield_v_size_adjustment = (stable_catcher_y_position - stable_fruit_start_position) / CatchPlayfield.HEIGHT;
+                const float playfield_v_catcher_offset = stable_catcher_y_position - CatchPlayfield.HEIGHT;
 
-                Scale = new Vector2(Parent.ChildSize.X / CatchPlayfield.WIDTH);
-                Position = new Vector2(0, -100 * stable_v_offset_ratio + Scale.X);
-                Size = Vector2.Divide(new Vector2(1, stable_v_offset_ratio), Scale);
+                Scale = new Vector2(Parent!.ChildSize.X / CatchPlayfield.WIDTH);
+                Position = new Vector2(0f, playfield_v_catcher_offset * Scale.Y);
+                Size = Vector2.Divide(new Vector2(1, playfield_v_size_adjustment), Scale);
             }
         }
     }