Replace box variants with a moveable adhesion property

Collapse the spiky/sticky/skewer box-variant assets into a single per-
instance `adhesion` property on any moveable block, chosen in the editor
via a dropdown next to the colour picker and stored in the .sav alongside
the class.

- spiky -> sticky: soft grab on every true edge (goopy shader)
- skewer -> gluey: rigid weld on every true edge (spiked outline)
- old trailing-face sticky is removed; its saves fold into new sticky

Move the spike geometry + drawGlueySprite into shaders.lua, fold drawing
and the adhesion flag into GenericMoveable, and delete the three
Generic{Sticky,Spiky,Skewer} classes and box_variants.lua. Room:createEntity
normalises legacy spiky_/skewer_/sticky_ class prefixes so old saves load,
and serialization emits `adhesion`. World/map previews and the movement
proxy follow the rename.

Backfill rooms/*.sav to the new format via tools/backfill_adhesion.lua
(41 objects across 8 files). Update tests to the two-mode model; the two
tests asserting the removed lateral-shear limitation are dropped and a
legacy-load migration test added. 27/27 pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

level_editor/editor.lua

@@ -63,6 +63,15 @@ local boxPaletteOpen = false
 local boxPaletteScroll = { scroll = 0 }
 local boxPaletteSections = {}
 
+-- Adhesion applied to any moveable block placed from the room view. "regular"
+-- means no adhesion; the others attach as a per-instance property (see
+-- Room:createEntity). `adhesionRect` is recomputed each frame in
+-- layoutRoomControls so draw and hit-testing agree; the menu expands upward.
+local adhesionOptions = { "regular", "sticky", "gluey" }
+local selectedAdhesion = "regular"
+local adhesionMenuOpen = false
+local adhesionRect = nil
+
 -- Note authoring state. `noteMode` is nil normally, "create" while placing a new
 -- note (click a cell to drop it and finish), or "edit" while retyping an
 -- existing note (with Save / Discard). `editingNote` is the note being edited.
@@ -87,7 +96,10 @@ end
 
 local function paintRoomCell(cell, button)
 	if button == 1 and selectedAsset then
-		currentRoom:attemptPlaceAtCell(selectedAsset, gameAssets[selectedAsset], cell, selectedColor)
+		-- adhesion is a no-op on non-moveable assets (Room:createEntity only reads
+		-- it in the moveable branch), so it is always safe to pass along.
+		local adhesion = selectedAdhesion ~= "regular" and selectedAdhesion or nil
+		currentRoom:attemptPlaceAtCell(selectedAsset, gameAssets[selectedAsset], cell, selectedColor, nil, adhesion)
 	elseif button == 2 then
 		currentRoom:attemptDeleteAtCell(cell, selectedColor)
 	end
@@ -132,16 +144,16 @@ local function currentRoomList()
 end
 
 local function rebuildBoxPaletteSections()
+	-- Adhesion (sticky/gluey) is now a placement modifier chosen with the dropdown
+	-- next to the colour picker, not a separate asset, so the palette lists only
+	-- the base box shapes (plus the barrier).
 	boxPaletteSections = {}
-	for _, prefix in ipairs({ "box", "spiky", "sticky", "skewer" }) do
-		local names = {}
-		local pattern = prefix == "box" and "^box" or "^" .. prefix .. "_box"
-		for name in pairs(gameAssets) do
-			if name:match(pattern) then table.insert(names, name) end
-		end
-		table.sort(names)
-		table.insert(boxPaletteSections, { prefix = prefix, names = names })
+	local names = {}
+	for name in pairs(gameAssets) do
+		if name:match("^box") then table.insert(names, name) end
 	end
+	table.sort(names)
+	table.insert(boxPaletteSections, { prefix = "box", names = names })
 	if gameAssets.player_blocker then
 		table.insert(boxPaletteSections, { prefix = "barrier", names = {"player_blocker"} })
 	end
@@ -213,15 +225,7 @@ local function drawPaletteAsset(name, x, y, size)
 	for color, path in pairs(props.sprites) do
 		local sprite = loadSprite(path)
 		love.graphics.setColor(gColor[color]:set())
-		if props.goopy and drawGoopySprite then
-			drawGoopySprite(sprite, drawX, drawY, scale)
-		elseif props.skewer and drawSkewerSprite then
-			drawSkewerSprite(sprite, props.cells and props.cells[color], drawX, drawY, scale)
-		elseif props.spiky and drawSpikySprite then
-			drawSpikySprite(sprite, props.cells and props.cells[color], drawX, drawY, scale)
-		else
-			love.graphics.draw(sprite, drawX, drawY, 0, scale, scale)
-		end
+		love.graphics.draw(sprite, drawX, drawY, 0, scale, scale)
 	end
 end
 
@@ -332,11 +336,89 @@ local function layoutRoomControls(c, s)
 		y = y + target + vgap
 	end
 
-	placeRow({ "white", "red", "green", "blue" }, 22)
+	-- Colour swatches with the adhesion dropdown packed to their right, centered
+	-- as one group. adhesionRect feeds both the dropdown draw and its hit-test.
+	do
+		local target = 22
+		local dropdownW = 78
+		local btns, total = {}, 0
+		for _, name in ipairs({ "white", "red", "green", "blue" }) do
+			local b = sizeBtn(name, target)
+			if b then table.insert(btns, b); total = total + b.w end
+		end
+		total = total + hgap * #btns + dropdownW
+		local x = c.x + (c.w - total) / 2
+		for _, b in ipairs(btns) do
+			b.x = x
+			b.y = y + (target - b.h) / 2
+			x = x + b.w + hgap
+		end
+		adhesionRect = { x = x, y = y, w = dropdownW, h = target }
+		y = y + target + vgap
+	end
 	placeRow({ "quick_player", "quick_static_wall", "quick_switch", "quick_door", "quick_wired_switch", "quick_wired_door", "quick_box" }, 22)
 	placeRow({ "save", "clearSaves", "world", "wire", "note", "mark" }, 28)
 end
 
+-- Stacked option rows for the open adhesion menu, expanding upward from the
+-- closed control so it never spills past the bottom edge. Shared by draw + click.
+local function adhesionMenuRects()
+	if not adhesionRect then return {} end
+	local rects = {}
+	for index, name in ipairs(adhesionOptions) do
+		-- topmost option is the last one drawn highest above the closed control
+		local offset = (#adhesionOptions - index + 1) * adhesionRect.h
+		rects[index] = {
+			name = name,
+			x = adhesionRect.x,
+			y = adhesionRect.y - offset,
+			w = adhesionRect.w,
+			h = adhesionRect.h,
+		}
+	end
+	return rects
+end
+
+local function drawAdhesionDropdown()
+	if not adhesionRect then return end
+	local r = adhesionRect
+	love.graphics.setColor(gColor.white:set())
+	love.graphics.setLineWidth(2)
+	love.graphics.rectangle("line", r.x, r.y, r.w, r.h)
+	local caret = adhesionMenuOpen and " v" or " ^"
+	love.graphics.printf(selectedAdhesion:upper() .. caret, r.x, r.y + (r.h - font:getHeight()) / 2, r.w, "center")
+	if adhesionMenuOpen then
+		for _, option in ipairs(adhesionMenuRects()) do
+			love.graphics.setColor(0, 0, 0, 0.9)
+			love.graphics.rectangle("fill", option.x, option.y, option.w, option.h)
+			love.graphics.setColor(option.name == selectedAdhesion and 1 or 0.6, 0.85, option.name == selectedAdhesion and 0.2 or 0.6, 1)
+			love.graphics.rectangle("line", option.x, option.y, option.w, option.h)
+			love.graphics.setColor(gColor.white:set())
+			love.graphics.printf(option.name:upper(), option.x, option.y + (option.h - font:getHeight()) / 2, option.w, "center")
+		end
+	end
+end
+
+-- Returns true when the click was consumed by the dropdown (toggle or a choice).
+local function adhesionDropdownClick(x, y)
+	if not adhesionRect then return false end
+	if adhesionMenuOpen then
+		for _, option in ipairs(adhesionMenuRects()) do
+			if Layout.hit(option, x, y) then
+				selectedAdhesion = option.name
+				adhesionMenuOpen = false
+				return true
+			end
+		end
+	end
+	if Layout.hit(adhesionRect, x, y) then
+		adhesionMenuOpen = not adhesionMenuOpen
+		return true
+	end
+	if adhesionMenuOpen then adhesionMenuOpen = false end
+	return false
+end
+
 -- Build the full room-view layout (sections + a scroll list + a back/search
 -- header) without drawing.  Shared by editorDraw and editorMouseHandler.
 local function buildRoomLayout()
@@ -402,10 +484,6 @@ local function rebuildAssetSearchButtons()
 		for color, location in pairs(gameAssets[asset].sprites) do sprites[color] = love.graphics.newImage(location) end
 		table.insert(assetSearchButtons, createUIElement{
 			sprites = sprites,
-			goopy = gameAssets[asset].goopy,
-			skewer = gameAssets[asset].skewer,
-			spiky = gameAssets[asset].spiky,
-			cells = gameAssets[asset].cells,
 			name = "asset",
 			text = asset,
 			x = 30,
@@ -739,10 +817,6 @@ function _initLevelEditor()
 			_addUIButton(createUIElement{
 				name = "quick_" .. asset,
 				sprites = sprites,
-				goopy = properties.goopy,
-				skewer = properties.skewer,
-				spiky = properties.spiky,
-				cells = properties.cells,
 				onClic = { left = function() selectQuickAsset(asset) end },
 				x = 0,
 				y = 0,
@@ -819,10 +893,6 @@ function selectFolder(folder)
 		-- each frame from the list section (see buildRoomLayout).
 		table.insert(assetListButtons, createUIElement{
 			sprites = sprites,
-			goopy = gameAssets[asset].goopy,
-			skewer = gameAssets[asset].skewer,
-			spiky = gameAssets[asset].spiky,
-			cells = gameAssets[asset].cells,
 			name = "asset",
 			text = asset,
 			x = 30,
@@ -1147,10 +1217,6 @@ function editAsset(asset)
 	local assetButton = createUIElement{
 		name = asset,
 		sprites = assetSprites,
-		goopy = assetProperties.goopy,
-		skewer = assetProperties.skewer,
-		spiky = assetProperties.spiky,
-		cells = assetProperties.cells,
 		x = sb.w / 2 - 18,
 		y = 80,
 	}	
@@ -1517,6 +1583,10 @@ function editorMouseHandler(x, y, button)
 				end
 			end
 
+			-- adhesion dropdown (sits next to the colour picker; its open menu
+			-- overlaps the area above the controls, so test it before the buttons)
+			if button == 1 and adhesionDropdownClick(x, y) then return end
+
 			-- control cluster (only the buttons that live there)
 			for _, name in ipairs({ "roomName", "white", "red", "green", "blue", "quick_player", "quick_static_wall", "quick_switch", "quick_door", "quick_wired_switch", "quick_wired_door", "quick_box", "save", "clearSaves", "world", "wire", "note", "mark" }) do
 				local b = uiButtons[name]
@@ -1833,6 +1903,9 @@ function editorDraw()
 			end
 		end
 
+		-- adhesion dropdown, drawn last so its open menu sits above the controls
+		drawAdhesionDropdown()
+
 		-- status strip between the list and the controls: Save / Discard while
 		-- editing an existing note, otherwise the ordinary status line.
 		if noteMode == "edit" then

level_editor/gui.lua

@@ -9,10 +9,6 @@ function GUI:initialize(t)
 	self.offset = {x = 0, y = 0}
 	self.name = t.name
 	self.text = t.text
-	self.goopy = t.goopy or false
-	self.skewer = t.skewer or false
-	self.spiky = t.spiky or false
-	self.cells = t.cells
 
 	if not t.onClic then
 		t.onClic = {}
@@ -103,15 +99,7 @@ function GUI:draw()
 	if self.sprites then
 		for color, sprite in pairs(self.sprites) do
 			love.graphics.setColor(gColor[color]:set())
-			if self.goopy and drawGoopySprite then
-				drawGoopySprite(sprite, box.x, box.y, self.scale)
-			elseif self.skewer and drawSkewerSprite then
-				drawSkewerSprite(sprite, self.cells and self.cells[color], box.x, box.y, self.scale)
-			elseif self.spiky and drawSpikySprite then
-				drawSpikySprite(sprite, self.cells and self.cells[color], box.x, box.y, self.scale)
-			else
-				love.graphics.draw(sprite, box.x, box.y, 0, self.scale, self.scale)
-			end
+			love.graphics.draw(sprite, box.x, box.y, 0, self.scale, self.scale)
 		end
 	end
 

level_editor/object_attributes.lua

@@ -1,7 +1,5 @@
 require "libs/TSerial"
 
-local BoxVariants = require "box_variants"
-
 local targetFolder = "art"
 local reanalyzeCells = true
 
@@ -77,5 +75,5 @@ function getAllAssets()
 	synthetic("wired_switch", "switch", "wired_switch")
 	synthetic("wired_door", "door", "wired_door")
 
-	return BoxVariants.addTo(globalAssetProperties)
+	return globalAssetProperties
 end