diff --git a/Source/Core/IO/DoomMapSetIO.cs b/Source/Core/IO/DoomMapSetIO.cs
index 52b4a2f..3e738ce 100644
--- a/Source/Core/IO/DoomMapSetIO.cs
+++ b/Source/Core/IO/DoomMapSetIO.cs
@@ -105,6 +105,7 @@ namespace CodeImp.DoomBuilder.IO
         public override int SlopeVertexType { get { return 9500; } }
         public override int Custom3DFloorType { get { return 160; } }
         public override int ColormapType { get { return -1; } }
+        public override int FlatAlignmentType { get { return -1; } }
 
         #endregion
 
diff --git a/Source/Core/IO/HexenMapSetIO.cs b/Source/Core/IO/HexenMapSetIO.cs
index 5ee63a3..c76b9cf 100644
--- a/Source/Core/IO/HexenMapSetIO.cs
+++ b/Source/Core/IO/HexenMapSetIO.cs
@@ -105,6 +105,7 @@ namespace CodeImp.DoomBuilder.IO
         public override int SlopeVertexType { get { return 9500; } }
         public override int Custom3DFloorType { get { return 160; } }
         public override int ColormapType { get { return -1; } }
+        public override int FlatAlignmentType { get { return -1; } }
 
         #endregion
 
diff --git a/Source/Core/IO/IMapSetIO.cs b/Source/Core/IO/IMapSetIO.cs
index 82d72ba..e1387bf 100644
--- a/Source/Core/IO/IMapSetIO.cs
+++ b/Source/Core/IO/IMapSetIO.cs
@@ -77,5 +77,6 @@ namespace CodeImp.DoomBuilder.IO
         int SlopeVertexType { get; }
         int Custom3DFloorType { get; }
         int ColormapType { get; }
+        int FlatAlignmentType { get; }
     }
 }
diff --git a/Source/Core/IO/MapSetIO.cs b/Source/Core/IO/MapSetIO.cs
index 2425cb3..cf5935d 100644
--- a/Source/Core/IO/MapSetIO.cs
+++ b/Source/Core/IO/MapSetIO.cs
@@ -98,6 +98,7 @@ namespace CodeImp.DoomBuilder.IO
         public abstract int SlopeVertexType { get; }
         public abstract int Custom3DFloorType { get; }
         public abstract int ColormapType { get; }
+        public abstract int FlatAlignmentType { get; }
 
         #endregion
 
diff --git a/Source/Core/IO/SRB2MapSetIO.cs b/Source/Core/IO/SRB2MapSetIO.cs
index 377143a..288fb00 100644
--- a/Source/Core/IO/SRB2MapSetIO.cs
+++ b/Source/Core/IO/SRB2MapSetIO.cs
@@ -143,6 +143,7 @@ namespace CodeImp.DoomBuilder.IO
         public override int MaxThingHeight { get { return 4095; } }
         public override int MinThingHeight { get { return 0; } }
         public override int ColormapType { get { return 606; } }
+        public override int FlatAlignmentType { get { return 7; } }
         #endregion
 
         #region ================== Reading
diff --git a/Source/Core/IO/UniversalMapSetIO.cs b/Source/Core/IO/UniversalMapSetIO.cs
index 4d75c57..a1045e5 100644
--- a/Source/Core/IO/UniversalMapSetIO.cs
+++ b/Source/Core/IO/UniversalMapSetIO.cs
@@ -155,6 +155,7 @@ namespace CodeImp.DoomBuilder.IO
         public override int SlopeVertexType { get { return 9500; } }
         public override int Custom3DFloorType { get { return 160; } }
         public override int ColormapType { get { return -1; } }
+        public override int FlatAlignmentType { get { return -1; } }
 
         #endregion
 
diff --git a/Source/Core/Map/Linedef.cs b/Source/Core/Map/Linedef.cs
index 06edde7..2489dd1 100644
--- a/Source/Core/Map/Linedef.cs
+++ b/Source/Core/Map/Linedef.cs
@@ -96,6 +96,7 @@ namespace CodeImp.DoomBuilder.Map
         public bool IsSlopeCopy { get { return General.Map.FormatInterface.SlopeCopyTypes.ContainsKey(Action); } }
         public bool IsVertexSlope { get { return General.Map.FormatInterface.VertexSlopeTypes.ContainsKey(Action); } }
         public bool IsColormap { get { return Action == General.Map.FormatInterface.ColormapType; } }
+        public bool IsFlatAlignment { get { return Action == General.Map.FormatInterface.FlatAlignmentType; } }
         public int Tag { get { return tags[0]; } set { BeforePropsChange(); tags[0] = value; if((value < General.Map.FormatInterface.MinTag) || (value > General.Map.FormatInterface.MaxTag)) throw new ArgumentOutOfRangeException("Tag", "Invalid tag number"); } } //mxd
 		public List<int> Tags { get { return tags; } set { BeforePropsChange(); tags = value; } } //mxd
 		public float LengthSq { get { return lengthsq; } }
diff --git a/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs b/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
index eff65a8..dd75d0f 100644
--- a/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
+++ b/Source/Plugins/BuilderModes/VisualModes/BaseVisualMode.cs
@@ -833,11 +833,12 @@ namespace CodeImp.DoomBuilder.BuilderModes
 				}
 			}
 
-            if (!General.Map.SRB2)
+            foreach (Sector s in General.Map.Map.Sectors)
             {
-                // Find sectors with 3 vertices, because they can be sloped
-                foreach (Sector s in General.Map.Map.Sectors)
+                if (General.Map.SRB2) s.Fields.Clear(); //Reset fake UDMF properties (since the linedef special that set them might no longer be there)
+                else
                 {
+                    // Find sectors with 3 vertices, because they can be sloped
                     // ========== Thing vertex slope, vertices with UDMF vertex offsets ==========
                     if (s.Sidedefs.Count == 3)
                     {
@@ -950,6 +951,62 @@ namespace CodeImp.DoomBuilder.BuilderModes
 
                 if (General.Map.SRB2)
                 {
+                    //MascaraSnake: Flat alignment
+                    if (l.IsFlatAlignment)
+                    {
+                        int sectortag = l.Tag;
+                        bool alignonlyceiling = l.IsFlagSet("2");
+                        bool alignonlyfloor = l.IsFlagSet("64");
+                        bool rotate = l.IsFlagSet("512");
+                        bool rotateonlyceiling = l.IsFlagSet("1024");
+                        bool rotateonlyfloor = l.IsFlagSet("16384");
+
+                        if (sectortags.ContainsKey(sectortag))
+                        {
+                            List<Sector> sectors = sectortags[sectortag];
+                            foreach (Sector s in sectors)
+                            {
+                                s.Fields.BeforeFieldsChange();
+                                if (rotate)
+                                {
+                                    float rotation = l.AngleDeg;
+
+                                    if (!rotateonlyceiling)
+                                    {
+                                        if (s.Fields.ContainsKey("rotationfloor")) s.Fields["rotationfloor"] = new UniValue(UniversalType.Float, rotation);
+                                        else s.Fields.Add("rotationfloor", new UniValue(UniversalType.Float, rotation));
+                                    }
+                                    if (!rotateonlyfloor)
+                                    {
+                                        if (s.Fields.ContainsKey("rotationceiling")) s.Fields["rotationceiling"] = new UniValue(UniversalType.Float, rotation);
+                                        else s.Fields.Add("rotationceiling", new UniValue(UniversalType.Float, rotation));
+                                    }
+                                }
+                                else
+                                {
+                                    float xoffset = l.Rect.Width;
+                                    float yoffset = l.Rect.Height;
+
+                                    if (!alignonlyceiling)
+                                    {
+                                        if (s.Fields.ContainsKey("xpanningfloor")) s.Fields["xpanningfloor"] = new UniValue(UniversalType.Float, xoffset);
+                                        else s.Fields.Add("xpanningfloor", new UniValue(UniversalType.Float, xoffset));
+                                        if (s.Fields.ContainsKey("ypanningfloor")) s.Fields["ypanningfloor"] = new UniValue(UniversalType.Float, yoffset);
+                                        else s.Fields.Add("ypanningfloor", new UniValue(UniversalType.Float, yoffset));
+                                    }
+                                    if (!alignonlyfloor)
+                                    {
+                                        if (s.Fields.ContainsKey("xpanningceiling")) s.Fields["xpanningceiling"] = new UniValue(UniversalType.Float, xoffset);
+                                        else s.Fields.Add("xpanningceiling", new UniValue(UniversalType.Float, xoffset));
+                                        if (s.Fields.ContainsKey("ypanningceiling")) s.Fields["ypanningceiling"] = new UniValue(UniversalType.Float, yoffset);
+                                        else s.Fields.Add("ypanningceiling", new UniValue(UniversalType.Float, yoffset));
+                                    }
+                                }
+                            }
+
+                        }
+                    }
+
                     //MascaraSnake: Colormap
                     if (l.IsColormap && l.Front != null)
                     {