Refactor backend into domain-first slices

apps/backend/Shared/Runtime/Vector3.cs

@@ -0,0 +1,36 @@
+namespace SpaceGame.Api.Shared.Runtime;
+
+public readonly record struct Vector3(float X, float Y, float Z)
+{
+    public static Vector3 Zero => new(0f, 0f, 0f);
+
+    public float DistanceTo(Vector3 other)
+    {
+        var dx = X - other.X;
+        var dy = Y - other.Y;
+        var dz = Z - other.Z;
+        return MathF.Sqrt((dx * dx) + (dy * dy) + (dz * dz));
+    }
+
+    public float LengthSquared() => (X * X) + (Y * Y) + (Z * Z);
+
+    public Vector3 MoveToward(Vector3 target, float maxDistance)
+    {
+        var delta = target.Subtract(this);
+        var distance = MathF.Sqrt(delta.LengthSquared());
+        if (distance <= 0.0001f || distance <= maxDistance)
+        {
+            return target;
+        }
+
+        var scale = maxDistance / distance;
+        return new Vector3(
+            X + (delta.X * scale),
+            Y + (delta.Y * scale),
+            Z + (delta.Z * scale));
+    }
+
+    public Vector3 Subtract(Vector3 other) => new(X - other.X, Y - other.Y, Z - other.Z);
+
+    public Vector3 Divide(float scalar) => MathF.Abs(scalar) <= 0.0001f ? Zero : new Vector3(X / scalar, Y / scalar, Z / scalar);
+}