diff --git a/CHANGELOG.md b/CHANGELOG.md
index c20156a..370cd5e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -82,6 +82,14 @@ The native shim's ABI is tracked separately by `b2Version()` (currently `2`).
     float**, **spin-lock**, **fixed ↔ free movement**, plus per-object specials
     (fan direction/strength/zone size, magnet pull/push/strength/reach, bomb blast
     radius/power and fuse). Everything round-trips through the save file.
+  - **Duplicate tool.** Click any part to drop an identical copy — same size,
+    colour, material and special settings — then drag it into place (it auto-selects
+    and switches to the Drag tool).
+  - **Reset.** A one-click "Reset" returns every part to exactly where it was the
+    moment you last pressed Run, so you can replay a contraption again and again.
+  - **Clearer Build vs Run.** The top accent turns amber and the subtitle reads
+    "RUNNING" while the simulation is live (green/neutral while building), and
+    picking any build tool while running drops you straight back into Build mode.
   - **New objects, all built from existing Kit primitives:** **helium balloons**
     (rise via negative gravity scale; lift parts by a rope; pop in a blast),
     **bombs** (detonate on a hard hit, a pressure-plate signal, or an optional
diff --git a/examples/box2dxt-contraption-builder.livecodescript b/examples/box2dxt-contraption-builder.livecodescript
index e13fc97..2cc70dc 100644
--- a/examples/box2dxt-contraption-builder.livecodescript
+++ b/examples/box2dxt-contraption-builder.livecodescript
@@ -1243,9 +1243,10 @@ local gRingN, gRingX, gRingY, gRingF
 local gDynParts, gDynDirty
 -- selection / inspector / onboarding / stress-test bookkeeping
 local gSelPart, gHoverId, gOnbStep, gStressCount
+local gPreRun                          -- snapshot of the build, taken when Run starts
 
-constant kShapeTools   = "drag,box,ball,capsule,poly,image,anchor,delete"
-constant kShapeLabels  = "Drag,Box,Ball,Capsule,Poly,Image,Anchor,Delete"
+constant kShapeTools   = "drag,box,ball,capsule,poly,image,anchor,delete,duplicate"
+constant kShapeLabels  = "Drag,Box,Ball,Capsule,Poly,Image,Anchor,Delete,Duplicate"
 constant kSpecialTools = "balloon,bomb,plate,fan,magnet"
 constant kSpecialLabels = "Balloon,Bomb,Pressure Plate,Fan,Magnet"
 constant kJointTools   = "hinge,weld,rope,slider,wheel"
@@ -1259,7 +1260,7 @@ constant kTopBarH = 54, kAccentH = 3
 constant kPaletteW = 196, kInspectorW = 248, kStatusH = 26
 constant kCanvasInset = 2, kGroundBarH = 22
 constant kPalPadX = 12, kPalBtnH = 26, kPalBtnGap = 4
-constant kPalSectionGap = 12, kPalHeaderH = 18
+constant kPalSectionGap = 8, kPalHeaderH = 18
 
 -- Materials, motors, feedback timing, and default part sizes (were magic numbers).
 constant kBounceOn = 0.7, kFlashMs = 150, kSelectLine = 3
@@ -1405,9 +1406,9 @@ on makeTopBar
    makeBar "ui_accent", 0, kTopBarH, tWide, kTopBarH + kAccentH, "72,190,130"
    makeLabel "ui_title", 18, 7, 280, 33, "Box2Dxt", 22, "236,238,245", true
    makeLabel "ui_sub", 20, 32, 560, 50, "Contraption Builder — build a machine, then press Run to bring it to life", 11, "150,154,166", false
-   put "mode,clear,save,load,recipes,info" into tIds
-   put "Run,Clear,Save,Load,Recipes,?" into tLbls
-   put "84,64,64,64,84,30" into tWidths
+   put "mode,reset,clear,save,load,recipes,info" into tIds
+   put "Run,Reset,Clear,Save,Load,Recipes,?" into tLbls
+   put "84,60,64,64,64,84,30" into tWidths
    put 6 into tGap
    put 0 into tW
    repeat for each item tId in tWidths
@@ -1631,6 +1632,7 @@ on highlightGroup pPrefix, pItems, pActiveId, pEnabled, pActiveColor
 end highlightGroup
 
 on highlightActions
+   local tAccent, tSub
    if there is a button "ui_act_mode" then
       if gMode is "run" then
          set the label of button "ui_act_mode" to "Build"
@@ -1641,6 +1643,17 @@ on highlightActions
       end if
       set the textColor of button "ui_act_mode" to "255,255,255"
    end if
+   -- A clear, full-width cue for which mode you're in: green accent + neutral
+   -- subtitle while building; amber accent + a "running" subtitle while simulating.
+   if gMode is "run" then
+      put "232,150,60" into tAccent
+      put "RUNNING — drag parts to play; press Build or Reset to edit" into tSub
+   else
+      put "72,190,130" into tAccent
+      put "Contraption Builder — build a machine, then press Run to bring it to life" into tSub
+   end if
+   if there is a graphic "ui_accent" then set the backgroundColor of graphic "ui_accent" to tAccent
+   if there is a field "ui_sub" then set the text of field "ui_sub" to tSub
    setToggle "ui_act_motor", gMotorOn
    setToggle "ui_act_bouncy", gBouncy
 end highlightActions
@@ -1687,6 +1700,10 @@ on mouseDown
       end if
       exit mouseDown
    end if
+   if gTool is "duplicate" then
+      if tHit is not empty then duplicatePart tHit
+      exit mouseDown
+   end if
    if tHit is not empty then
       put tHit into gDragCtrl
       put "build" into gDragMode
@@ -1748,6 +1765,8 @@ on handleUiClick
       hideRecipesMenu
       exit handleUiClick
    end if
+   -- Picking a build tool while the simulation runs drops you back into Build.
+   if ("ui_tool_" is in tName or "ui_joint_" is in tName) and gMode is "run" then toggleMode
    if "ui_tool_" is in tName then
       put the uToolId of the target into gTool
       put empty into gJointTool
@@ -1778,6 +1797,9 @@ on handleAction pId
       case "mode"
          toggleMode
          break
+      case "reset"
+         resetMachine
+         break
       case "clear"
          clearAll
          break
@@ -1855,6 +1877,7 @@ end handleAction
 
 on toggleMode
    if gMode is "build" then
+      put serializeText() into gPreRun   -- remember the layout so Reset can restore it
       put "run" into gMode
       put empty into gJointTool
       resetPend
@@ -2462,6 +2485,35 @@ on deletePart pCtrl
    put "Deleted a part and any joints on it." into gStatus
 end deletePart
 
+-- Drop an identical copy of a part — same size, colour, material and special
+-- settings — nudged off the original, then select it and switch to Drag so it
+-- can be moved straight away. (Joints aren't copied; they connect two parts.)
+on duplicatePart pCtrl
+   if pCtrl is empty then exit duplicatePart
+   if pCtrl is not among the lines of gParts then exit duplicatePart
+   local tKind, tLoc, tNx, tNy, tNew
+   put the uKind of pCtrl into tKind
+   put the loc of pCtrl into tLoc
+   put (item 1 of tLoc) + 26 into tNx
+   put (item 2 of tLoc) + 26 into tNy
+   if tNx > gArenaR then put (item 1 of tLoc) - 26 into tNx
+   if tNy > gArenaB then put (item 2 of tLoc) - 26 into tNy
+   put rebuildPart(tKind, tNx, tNy, (the width of pCtrl), (the height of pCtrl), \
+         (the uColor of pCtrl), (the uFile of pCtrl)) into tNew
+   if tNew is empty then exit duplicatePart
+   if the uBounce of pCtrl is not empty then
+      set the uBounce of tNew to (the uBounce of pCtrl)
+      if (the uBounce of pCtrl) > 0 then b2kSetBounce tNew, (the uBounce of pCtrl)
+   end if
+   applyPartSpecial tNew, partSpecial(pCtrl)
+   renderBuild
+   put "drag" into gTool
+   selectPart tNew
+   highlightAll
+   put "Duplicated a " & friendlyKind(tKind) & ". Drag the copy where you want it." into gStatus
+   updateHud
+end duplicatePart
+
 on removeJointAt pIndex
    try
       b2kRemoveJoint gJHandle[pIndex]
@@ -2576,7 +2628,8 @@ end buildSampleSwing
 -- =====================================================================
 -- Save / load (whole contraption as tab-delimited text)
 -- =====================================================================
-on saveContraption
+-- Serialise the whole scene to CB2 text (used by Save and by Reset's snapshot).
+function serializeText
    local tOut, tP, tI
    put "CB2" & cr into tOut
    repeat for each line tP in gParts
@@ -2590,6 +2643,12 @@ on saveContraption
          if gJKind[tI] is not empty then put jointLine(tI) & cr after tOut
       end repeat
    end if
+   return tOut
+end serializeText
+
+on saveContraption
+   local tOut
+   put serializeText() into tOut
    ask file "Save contraption as:" with "contraption.cbx"
    if it is empty or the result is "cancel" then
       put "Save cancelled." into gStatus
@@ -2684,9 +2743,7 @@ function jointLine pIndex
 end jointLine
 
 on loadContraption
-   local tFile, tData, tLine, tRec, tMap, tNew
-   local tId, tKind, tX, tY, tW, tH, tBounce, tColor, tFileRef, tSpecial
-   local tIdA, tIdB, tPx, tPy, tMotor, tA, tB
+   local tFile, tData
    answer file "Open a contraption:" with type "Contraption|cbx,txt"
    put it into tFile
    if tFile is empty or the result is "cancel" then
@@ -2706,10 +2763,21 @@ on loadContraption
       exit loadContraption
    end if
    if gMode is "run" then toggleMode
+   rebuildFromText tData
+   put "Loaded contraption from " & tFile & ". Press Run to simulate." into gStatus
+   updateHud
+end loadContraption
+
+-- Rebuild the whole scene from CB2/CB1 text, clearing the stage first. Shared by
+-- Load (from a file) and Reset (from the pre-run snapshot).
+on rebuildFromText pData
+   local tLine, tRec, tMap, tNew
+   local tId, tKind, tX, tY, tW, tH, tBounce, tColor, tFileRef, tSpecial
+   local tIdA, tIdB, tPx, tPy, tMotor, tA, tB
    clearAll
    put empty into tMap
    lock screen
-   repeat for each line tLine in tData
+   repeat for each line tLine in pData
       set the itemDelimiter to tab
       put item 1 of tLine into tRec
       if tRec is "part" then
@@ -2754,9 +2822,22 @@ on loadContraption
    set the itemDelimiter to comma
    renderBuild
    unlock screen
-   put "Loaded contraption from " & tFile & ". Press Run to simulate." into gStatus
+end rebuildFromText
+
+-- Restore the layout captured when Run last started, and return to Build mode.
+on resetMachine
+   if gPreRun is empty then
+      put "Nothing to reset yet — press Run first; then Reset brings this build back." into gStatus
+      updateHud
+      exit resetMachine
+   end if
+   lock screen
+   if gMode is "run" then toggleMode
+   rebuildFromText gPreRun
+   unlock screen
+   put "Reset to your pre-run build." into gStatus
    updateHud
-end loadContraption
+end resetMachine
 
 function rebuildPart pKind, pX, pY, pW, pH, pColor, pFile
    if pW is empty or pW < 1 then put kBoxMin into pW
@@ -3476,9 +3557,9 @@ on adjustPartProp pCtrl, pKey, pDir
          else resizePart pCtrl, 0.87
          break
       case "color"
-         put colorPalette() into tPal
+         put partSwatches() into tPal
          put the number of lines of tPal into tCnt
-         put colorIndex(pCtrl, tPal) + pDir into tIdx
+         put swatchIndexOf(pCtrl, tPal) + pDir into tIdx
          if tIdx < 1 then put tCnt into tIdx
          if tIdx > tCnt then put 1 into tIdx
          set the backgroundColor of pCtrl to (line tIdx of tPal)
@@ -3645,13 +3726,13 @@ on reapplyMaterial pCtrl
 end reapplyMaterial
 
 -- A generous palette the Colour setting cycles through.
-function colorPalette
+function partSwatches
    return "92,150,222" & cr & "84,206,142" & cr & "232,182,92" & cr & "214,92,92" & cr \
          & "206,124,206" & cr & "120,200,232" & cr & "236,120,150" & cr & "150,160,180" & cr \
          & "120,90,210" & cr & "240,140,60" & cr & "90,200,170" & cr & "232,232,236"
-end colorPalette
+end partSwatches
 
-function colorIndex pCtrl, pPal
+function swatchIndexOf pCtrl, pPal
    local tLine, tI
    put 0 into tI
    repeat for each line tLine in pPal
@@ -3659,7 +3740,7 @@ function colorIndex pCtrl, pPal
       if tLine is (the uColor of pCtrl) then return tI
    end repeat
    return 0
-end colorIndex
+end swatchIndexOf
 
 function frictionLabel pV
    if pV is empty then put 0.4 into pV
@@ -3708,6 +3789,7 @@ function niceName pId
    local tNames
    put "drag=Move / Drag" & cr & "box=Box" & cr & "ball=Ball" & cr & "capsule=Capsule" & cr \
          & "poly=Polygon" & cr & "image=Picture" & cr & "anchor=Anchor" & cr & "delete=Delete" & cr \
+         & "duplicate=Duplicate" & cr \
          & "balloon=Helium Balloon" & cr & "bomb=Bomb" & cr & "plate=Pressure Plate" & cr \
          & "fan=Fan / Wind" & cr & "magnet=Magnet" & cr & "hinge=Hinge Joint" & cr \
          & "weld=Weld Joint" & cr & "rope=Rope Joint" & cr & "slider=Slider Joint" & cr \
@@ -3729,7 +3811,7 @@ end niceName
 function toolGlyph pId
    local tGlyphs
    put "drag=✥" & cr & "box=■" & cr & "ball=●" & cr & "capsule=▬" & cr & "poly=◆" & cr \
-         & "image=▦" & cr & "anchor=▼" & cr & "delete=✕" & cr & "balloon=◯" & cr & "bomb=◉" & cr \
+         & "image=▦" & cr & "anchor=▼" & cr & "delete=✕" & cr & "duplicate=▣" & cr & "balloon=◯" & cr & "bomb=◉" & cr \
          & "plate=▭" & cr & "fan=▷" & cr & "magnet=◐" & cr & "hinge=○" & cr & "weld=▰" & cr \
          & "rope=∿" & cr & "slider=↔" & cr & "wheel=◎" into tGlyphs
    local tLine
@@ -3763,6 +3845,8 @@ function toolHelp pId
          return "Place a fixed point that never moves." & cr & "An anchor is pinned to the world. Attach joints to it to hold things up — perfect as a motor mount or a pivot."
       case "delete"
          return "Remove a part you click on." & cr & "Delete tool. Click any part to remove it, along with any joints attached to it."
+      case "duplicate"
+         return "Copy a part you click on." & cr & "Duplicate tool. Click any part to drop an identical copy — same size, colour and settings — then drag it where you want."
       case "balloon"
          return "A helium balloon that floats upward." & cr & "A balloon rises on its own. Tie it to a part with a Rope joint to lift that part. A nearby bomb blast pops it."
       case "bomb"
@@ -3791,6 +3875,8 @@ function actionHelp pId
    switch pId
       case "mode"
          return "Switch between Build (arrange) and Run (simulate)."
+      case "reset"
+         return "Put every part back where it was when you last pressed Run."
       case "clear"
          return "Remove everything and start with an empty stage."
       case "save"