diff --git a/applications/sudoku/digitseteditor.lfm b/applications/sudoku/digitseteditor.lfm
new file mode 100644
index 000000000..ee2930d41
--- /dev/null
+++ b/applications/sudoku/digitseteditor.lfm
@@ -0,0 +1,63 @@
+object DigitSetEditorForm: TDigitSetEditorForm
+  Left = 668
+  Height = 240
+  Top = 144
+  Width = 320
+  BorderStyle = bsDialog
+  Caption = 'DigitSetEditorForm'
+  ClientHeight = 240
+  ClientWidth = 320
+  KeyPreview = True
+  OnActivate = FormActivate
+  OnKeyPress = FormKeyPress
+  OnShow = FormShow
+  LCLVersion = '2.1.0.0'
+  object DigitCG: TCheckGroup
+    Left = 16
+    Height = 89
+    Top = 16
+    Width = 136
+    AutoFill = True
+    Caption = 'Digits'
+    ChildSizing.LeftRightSpacing = 6
+    ChildSizing.VerticalSpacing = 6
+    ChildSizing.EnlargeHorizontal = crsScaleChilds
+    ChildSizing.ShrinkHorizontal = crsScaleChilds
+    ChildSizing.ShrinkVertical = crsScaleChilds
+    ChildSizing.Layout = cclLeftToRightThenTopToBottom
+    ChildSizing.ControlsPerLine = 3
+    ClientHeight = 69
+    ClientWidth = 132
+    Columns = 3
+    Items.Strings = (
+      '1'
+      '2'
+      '3'
+      '4'
+      '5'
+      '6'
+      '7'
+      '8'
+      '9'
+    )
+    ParentBiDiMode = False
+    TabOrder = 0
+    Data = {
+      09000000020202020202020202
+    }
+  end
+  object btnOK: TButton
+    AnchorSideLeft.Control = DigitCG
+    AnchorSideRight.Control = DigitCG
+    AnchorSideRight.Side = asrBottom
+    Left = 16
+    Height = 25
+    Top = 112
+    Width = 136
+    Anchors = [akTop, akLeft, akRight]
+    Caption = '&Ok'
+    Default = True
+    ModalResult = 1
+    TabOrder = 1
+  end
+end
diff --git a/applications/sudoku/digitseteditor.pas b/applications/sudoku/digitseteditor.pas
new file mode 100644
index 000000000..f009d6209
--- /dev/null
+++ b/applications/sudoku/digitseteditor.pas
@@ -0,0 +1,95 @@
+unit DigitSetEditor;
+
+{$mode objfpc}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls, StdCtrls,
+  SudokuType;
+
+type
+
+  { TDigitSetEditorForm }
+
+  TDigitSetEditorForm = class(TForm)
+    btnOK: TButton;
+    DigitCG: TCheckGroup;
+    procedure FormActivate(Sender: TObject);
+    procedure FormKeyPress(Sender: TObject; var Key: char);
+    procedure FormShow(Sender: TObject);
+  private
+    FPreferredRight: Integer;
+    function GetDigitSet: TDigitSet;
+    procedure SetDigitSet(ASet: TDigitSet);
+    procedure SetRight({%H-}Data: PtrInt);
+
+  public
+    property DigitSet: TDigitSet read GetDigitSet write SetDigitSet;
+    property PreferredRight: Integer read FPreferredRight write FPreferredRight;
+  end;
+
+var
+  DigitSetEditorForm: TDigitSetEditorForm;
+
+implementation
+
+{$R *.lfm}
+
+{ TDigitSetEditorForm }
+
+procedure TDigitSetEditorForm.FormKeyPress(Sender: TObject; var Key: char);
+var
+  Digit: Integer;
+begin
+  if (Key in ['1'..'9']) then
+  begin
+    Digit := Ord(Key) - Ord('0');
+    DigitCG.Checked[Pred(Digit)] := not DigitCG.Checked[Pred(Digit)];
+    Key := #0;
+  end;
+  if (Key = #27) then //escape
+  begin
+    Key := #0;
+    ModalResult := mrCancel;
+  end;
+end;
+
+procedure TDigitSetEditorForm.FormShow(Sender: TObject);
+begin
+  Application.QueueAsyncCall(@SetRight, FPreferredRight)
+end;
+
+procedure TDigitSetEditorForm.FormActivate(Sender: TObject);
+begin
+  OnACtivate := nil;
+  ClientWidth := 2 * DigitCG.Left + DigitCG.Width;
+  ClientHeight := btnOK.Top + btnOK.Height + DigitCG.Top;
+end;
+
+function TDigitSetEditorForm.GetDigitSet: TDigitSet;
+var
+  i: Integer;
+begin
+  Result := [];
+  for i := 0 to DigitCG.Items.Count - 1 do
+    if DigitCG.Checked[i] then Include(Result, Succ(i));
+end;
+
+procedure TDigitSetEditorForm.SetDigitSet(ASet: TDigitSet);
+var
+  D: TDigits;
+begin
+  for D in TDigits do
+  begin
+    DigitCG.Checked[D-1] := (D in ASet);  //don't use Pred(D) here, gives RangeCheckError when D=1
+  end;
+end;
+
+procedure TDigitSetEditorForm.SetRight(Data: PtrInt);
+begin
+  Left := FPreferredRight - Width;
+end;
+
+end.
+
diff --git a/applications/sudoku/scratchpad.lfm b/applications/sudoku/scratchpad.lfm
index 8387ef25c..b21e9ca30 100644
--- a/applications/sudoku/scratchpad.lfm
+++ b/applications/sudoku/scratchpad.lfm
@@ -22,6 +22,8 @@ object ScratchForm: TScratchForm
     RowCount = 9
     ScrollBars = ssNone
     TabOrder = 0
+    OnClick = ScratchGridClick
+    OnPrepareCanvas = ScratchGridPrepareCanvas
   end
   object btnCopy: TButton
     AnchorSideLeft.Control = ScratchGrid
diff --git a/applications/sudoku/scratchpad.pas b/applications/sudoku/scratchpad.pas
index 002432b7a..bc0953ce9 100644
--- a/applications/sudoku/scratchpad.pas
+++ b/applications/sudoku/scratchpad.pas
@@ -6,7 +6,8 @@ interface
 
 uses
   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, Grids, StdCtrls,
-  SudokuType;
+  Math,
+  SudokuType, DigitSetEditor;
 
 type
 
@@ -20,12 +21,16 @@ type
     procedure btnCopyClick(Sender: TObject);
     procedure FormActivate(Sender: TObject);
     procedure FormCreate(Sender: TObject);
+    procedure ScratchGridClick(Sender: TObject);
+    procedure ScratchGridPrepareCanvas(sender: TObject; aCol, aRow: Integer;
+      {%H-}aState: TGridDrawState);
   private
     FRawData: TRawGrid;
     FOnCopyValues: TCopyValuesEvent;
     procedure SetRawData(Data: TRawGrid);
     procedure GridToValues(out Values: TValues);
     procedure KeepInView;
+    procedure EditCell(ACol, ARow: Integer);
   public
     property RawData: TRawGrid write SetRawData;
     property OnCopyValues: TCopyValuesEvent read FOnCopyValues write FOnCopyValues;
@@ -38,6 +43,51 @@ implementation
 
 {$R *.lfm}
 
+function DigitSetToStr(ASet: TDigitSet): String;
+  function Get(D: Integer): Char;
+  begin
+    if (D in ASet) then
+      Result := Char(Ord('0') + D)
+    else
+      Result := 'x';//#32;
+  end;
+begin
+  Result := Format('%s-%s-%s'+LineEnding+'%s-%s-%s'+LineEnding+'%s-%s-%s',[Get(1),Get(2),Get(3),Get(4),Get(5),Get(6),Get(7),Get(8),Get(9)]);
+end;
+
+function StrToDigitSet(const S: String): TDigitSet;
+var
+  Ch: Char;
+begin
+  Result := [];
+  for Ch in S do
+    if (Ch in ['1'..'9']) then
+      Include(Result, Ord(Ch) - Ord('0'));
+end;
+
+{
+
+}
+function TryCellTextToDigit(const AText: String; out Value: TDigits): Boolean;
+var
+  Ch: Char;
+  S: String;
+begin
+  Result := False;
+  S := '';
+  for Ch in AText do
+    if (Ch in ['1'..'9']) then S := S + Ch;
+  if (Length(S) = 1) then
+  begin
+    Ch := S[1];
+    if (Ch in ['1'..'9']) then
+    begin
+      Value := Ord(Ch) - Ord('0');
+      Result := True;
+    end;
+  end;
+end;
+
 { TScratchForm }
 
 procedure TScratchForm.FormActivate(Sender: TObject);
@@ -45,8 +95,14 @@ begin
   Self.OnActivate := nil;
   ScratchGrid.ClientWidth := 9 * ScratchGrid.DefaultColWidth;
   ScratchGrid.ClientHeight := 9 * ScratchGrid.DefaultRowHeight;
+  //writeln(format('ScratchGrid: %d x %d',[ScratchGrid.ClientWidth,ScratchGrid.ClientHeight]));
   ClientWidth := 2 * ScratchGrid.Left + ScratchGrid.Width;
-  ClientHeight := btnCopy.Top + btnCopy.Height + 10;
+  //writeln(format('btnCopy.Top: %d, btnCopy.Height: %d',[btnCopy.Top,btnCopy.Height]));
+  Self.ReAlign;
+  //ClientHeight := btnCopy.Top + btnCopy.Height + 10;
+  //Above doesn't work: at this time btnCopy.Top still holds designtime value, even when it's top is anchored to the grid
+  ClientHeight := ScratchGrid.Top + ScratchGrid.Height + 10 + btnCopy.Height + 10;
+  //writeln(format('ClientHeight: %d',[ClientHeight]));
   KeepInView;
 end;
 
@@ -61,8 +117,54 @@ begin
 end;
 
 procedure TScratchForm.FormCreate(Sender: TObject);
+var
+  DefWH: Integer;
 begin
-  ScratchGrid.DefaultColWidth := ScratchGrid.Canvas.TextWidth(' [1,2,3,4,5,6,7,8,9] ') + 8;
+  DefWH := Max(ScratchGrid.Canvas.TextWidth(' 8-8-8 '), 3 * ScratchGrid.Canvas.TextHeight('8')) + 10;
+  ScratchGrid.DefaultColWidth := DefWH;
+  ScratchGrid.DefaultRowHeight := DefWH;
+end;
+
+procedure TScratchForm.ScratchGridClick(Sender: TObject);
+var
+  Col, Row: Integer;
+begin
+  Col := ScratchGrid.Col;
+  Row := ScratchGrid.Row;
+  if not FRawData[Col+1,Row+1].Locked then
+    EditCell(Col, Row);
+end;
+
+procedure TScratchForm.ScratchGridPrepareCanvas(sender: TObject; aCol, aRow: Integer; aState: TGridDrawState);
+var
+  NeedsColor: Boolean;
+  GridTextStyle: TTextStyle;
+begin
+  GridTextStyle := (Sender as TStringGrid).Canvas.TextStyle;
+  GridTextStyle.Alignment := taCenter;
+  GridTextStyle.Layout := tlCenter;
+  GridTextStyle.SingleLine := False;
+  (Sender as TStringGrid).Canvas.TextStyle := GridTextStyle;
+  NeedsColor := False;
+  if aCol in [0..2, 6..8] then
+  begin
+    if aRow in [0..2, 6..8] then
+      NeedsColor := True;
+  end
+  else
+  begin
+    if aRow in [3..5] then
+      NeedsColor := True;
+  end;
+  if NeedsColor then
+    (Sender as TStringGrid).Canvas.Brush.Color := $00EEEEEE;
+  //if (aRow=0) and (aCol=0) then
+  if FRawData[aCol+1, aRow+1].Locked then
+  begin
+    (Sender as TStringGrid).Canvas.Brush.Color := $00F8E3CB; // $00F1CEA3;
+    (Sender as TStringGrid).Canvas.Font.Color := clRed;
+    (Sender as TStringGrid).Canvas.Font.Style := [fsBold]
+  end;
 end;
 
 procedure TScratchForm.SetRawData(Data: TRawGrid);
@@ -79,7 +181,8 @@ begin
       if Data[Col,Row].Locked then
         S := IntToStr(Data[Col,Row].Value)
       else
-        S := DbgS(Data[Col,Row].DigitsPossible);
+        //S := DbgS(Data[Col,Row].DigitsPossible);
+        S := DigitSetToStr(Data[Col,Row].DigitsPossible);
       ScratchGrid.Cells[Col-1,Row-1] := S;
     end;
   end;
@@ -88,7 +191,7 @@ end;
 procedure TScratchForm.GridToValues(out Values: TValues);
 var
   Col, Row: Integer;
-  AValue: Longint;
+  AValue: TDigits;
   S: String;
 begin
   Values := Default(TValues);
@@ -97,9 +200,10 @@ begin
     for Row := 0 to 8 do
     begin
       S := ScratchGrid.Cells[Col, Row];
+      //DigitSet := StrToDigitSet(S);
       if Length(S) >= 1 then
       begin
-        if TryStrToInt(S, AValue) then
+        if TryCellTextToDigit(S, AValue) then
           Values[Col + 1, Row + 1] := AValue;
       end;
     end;
@@ -119,5 +223,22 @@ begin
   Left := FL;
 end;
 
+procedure TScratchForm.EditCell(ACol, ARow: Integer);
+var
+  S: String;
+  DigitSet: TDigitSet;
+begin
+  S := ScratchGrid.Cells[ACol, ARow];
+  DigitSet := StrToDigitSet(S);
+  DigitSetEditorForm.DigitSet := DigitSet;
+  DigitSetEditorForm.Top := Top;
+  DigitSetEditorForm.PreferredRight := Left;
+  if (DigitSetEditorForm.ShowModal = mrOK) then
+  begin
+    S := DigitSetToStr(DigitSetEditorForm.DigitSet);
+    ScratchGrid.Cells[ACol, ARow] := S;
+  end;
+end;
+
 end.
 
diff --git a/applications/sudoku/sudoku.lpi b/applications/sudoku/sudoku.lpi
index c042e12c4..4c89073a4 100644
--- a/applications/sudoku/sudoku.lpi
+++ b/applications/sudoku/sudoku.lpi
@@ -15,11 +15,6 @@
       <Item2 Name="Debug">
         <CompilerOptions>
           <Version Value="11"/>
-          <Parsing>
-            <SyntaxOptions>
-              <UseAnsiStrings Value="False"/>
-            </SyntaxOptions>
-          </Parsing>
           <CodeGeneration>
             <Checks>
               <IOChecks Value="True"/>
@@ -60,7 +55,7 @@
         <PackageName Value="LCL"/>
       </Item1>
     </RequiredPackages>
-    <Units Count="4">
+    <Units Count="5">
       <Unit0>
         <Filename Value="sudoku.lpr"/>
         <IsPartOfProject Value="True"/>
@@ -71,6 +66,7 @@
         <ComponentName Value="Form1"/>
         <HasResources Value="True"/>
         <ResourceBaseClass Value="Form"/>
+        <UnitName Value="SudokuMain"/>
       </Unit1>
       <Unit2>
         <Filename Value="sudokutype.pas"/>
@@ -85,6 +81,13 @@
         <ResourceBaseClass Value="Form"/>
         <UnitName Value="ScratchPad"/>
       </Unit3>
+      <Unit4>
+        <Filename Value="digitseteditor.pas"/>
+        <IsPartOfProject Value="True"/>
+        <ComponentName Value="DigitSetEditorForm"/>
+        <ResourceBaseClass Value="Form"/>
+        <UnitName Value="DigitSetEditor"/>
+      </Unit4>
     </Units>
   </ProjectOptions>
   <CompilerOptions>
diff --git a/applications/sudoku/sudoku.lpr b/applications/sudoku/sudoku.lpr
index ffb00db69..950399d0e 100644
--- a/applications/sudoku/sudoku.lpr
+++ b/applications/sudoku/sudoku.lpr
@@ -27,12 +27,13 @@ program sudoku;
 uses
   Interfaces, // this includes the LCL widgetset
   Forms
-  { add your units here }, sudokumain, scratchpad;
+  { add your units here }, sudokumain, scratchpad, digitseteditor;
 
 begin
   Application.Initialize;
   Application.CreateForm(TForm1, Form1);
   Application.CreateForm(TScratchForm, ScratchForm);
+  Application.CreateForm(TDigitSetEditorForm, DigitSetEditorForm);
   Application.Run;
 end.
 
diff --git a/applications/sudoku/sudokumain.lfm b/applications/sudoku/sudokumain.lfm
index 7f02d3795..183cf7dde 100644
--- a/applications/sudoku/sudokumain.lfm
+++ b/applications/sudoku/sudokumain.lfm
@@ -23,7 +23,7 @@ object Form1: TForm1
     DefaultRowHeight = 30
     FixedCols = 0
     FixedRows = 0
-    Options = [goFixedVertLine, goFixedHorzLine, goVertLine, goHorzLine, goRangeSelect, goEditing, goSmoothScroll]
+    Options = [goFixedVertLine, goFixedHorzLine, goVertLine, goHorzLine, goEditing, goSmoothScroll]
     RowCount = 9
     ScrollBars = ssNone
     TabOrder = 2
diff --git a/applications/sudoku/sudokumain.pas b/applications/sudoku/sudokumain.pas
index b6e2f2742..9775d9391 100644
--- a/applications/sudoku/sudokumain.pas
+++ b/applications/sudoku/sudokumain.pas
@@ -1,4 +1,4 @@
-unit sudokumain;
+unit SudokuMain;
 
 {
  ***************************************************************************
@@ -267,8 +267,8 @@ procedure TForm1.ShowScratchPad(RawData: TRawGrid);
 begin
   ScratchForm.OnCopyValues := @OnCopyBackValues;
   ScratchForm.RawData := RawData;
-  ScratchForm.ScratchGrid.Options := SGrid.Options + [goEditing];
-  ScratchForm.ScratchGrid.OnPrepareCanvas := @Self.SGridPrepareCanvas;
+  ScratchForm.ScratchGrid.Options := SGrid.Options - [goEditing];
+  ScratchForm.Left := Left + Width + 10;
   ScratchForm.Show;
 end;