switch root namespace name to NITLOAD

src/Nitload.Mathematics/Geometries/PlainGeometry/Define/IPlainEntity.cs

@@ -0,0 +1,55 @@
+// -----------------------------------------------------------------------------
+// file="IPlainEntity"
+// Project: StgSharp
+// Copyright (c) Nitload.
+// SPDX-License-Identifier: MIT
+// -----------------------------------------------------------------------------
+
+using Nitload.Mathematics;
+using Nitload.Mathematics.Numeric.Graphics;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Nitload.Geometries
+{
+    public interface IPlainEntity
+    {
+
+        public Vec2 CenterPosition { get; set; }
+
+        public bool CollideWith(
+                    IPlainEntity entity
+        );
+
+    }
+
+    public class PlainEntity : IPlainEntity
+    {
+
+        private PlainGeometry _shape;
+
+        public PlainEntity(
+               PlainGeometry shape
+        )
+        {
+            _shape = shape;
+        }
+
+        bool IPlainEntity.CollideWith(
+                          IPlainEntity entity
+        )
+        {
+            throw new NotImplementedException();
+        }
+
+        Vec2 IPlainEntity.CenterPosition
+        {
+            get => _shape.Coordination.LocalOrigin.Coord.XY;
+            set => throw new InvalidOperationException();
+        }
+
+    }
+}