diff --git a/source/GM-TE/GMTEBrush.class.st b/source/GM-TE/GMTEBrush.class.st
index a97ea5c2..8f6a8d69 100644
--- a/source/GM-TE/GMTEBrush.class.st
+++ b/source/GM-TE/GMTEBrush.class.st
@@ -1,3 +1,6 @@
+"
+A GMTEBrush is responsible for returning a set of indices that are selected by the user and selecting the interchangeable algorithm for the execution.
+"
 Class {
 	#name : #GMTEBrush,
 	#superclass : #Object,
@@ -9,7 +12,8 @@ Class {
 		'firstMatrixIndex',
 		'outputSet'
 	],
-	#category : #'GM-TE-UI'
+	#category : #'GM-TE-UI',
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:49'
 }
 
 {
@@ -22,54 +26,58 @@ GMTEBrush class >> borderingOffsets [
 ]
 
 {
-	#category : #forms,
-	#'squeak_changestamp' : 'JS 7/11/2024 15:40'
+	#category : #brushHelper,
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:03'
 }
 GMTEBrush >> calculateOffsetsForRadius: aRadius [
     	
 	|offsets|
 	offsets := OrderedCollection new.
-    	(0-radius to: radius) do: [:dx |
-        	(0-radius to: radius) do: [:dy |
+    	(0-self radius to: self radius) do: [:dx |
+        	(0-self radius to: self radius) do: [:dy |
             	((dx squared + dy squared) <= aRadius squared) ifTrue: [offsets add: dx @ dy]]].
 
-	^offsets
+	^ offsets
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/6/2024 12:48'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:40'
 }
 GMTEBrush >> currentBrush [
+
 	^ currentBrush
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/6/2024 12:48'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:40'
 }
-GMTEBrush >> currentBrush: anObject [
-	currentBrush := anObject
+GMTEBrush >> currentBrush: aBrush [
+
+	currentBrush := aBrush
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/9/2024 08:47'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:41'
 }
 GMTEBrush >> currentMatrixIndex [
+
 	^ currentMatrixIndex
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/9/2024 08:47'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:41'
 }
-GMTEBrush >> currentMatrixIndex: anObject [
-	currentMatrixIndex := anObject
+GMTEBrush >> currentMatrixIndex: anIndex [
+
+	currentMatrixIndex := anIndex
 ]
 
 {
-	#category : #'as yet unclassified',
+	#category : #execute,
 	#'squeak_changestamp' : 'Valentin Teutschbein 7/11/2024 17:10'
 }
 GMTEBrush >> executeWithMatrixIndex: anIndex andLayer: aLayer [
@@ -81,8 +89,8 @@ GMTEBrush >> executeWithMatrixIndex: anIndex andLayer: aLayer [
 ]
 
 {
-	#category : #forms,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/11/2024 17:10'
+	#category : #brushes,
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:26'
 }
 GMTEBrush >> fillBrush [
 
@@ -95,51 +103,49 @@ GMTEBrush >> fillBrush [
 	self outputSet add: self currentMatrixIndex.
 	visited at: self currentMatrixIndex y at: self currentMatrixIndex x put: true.
 	
-	self fillDfsWithVisited: visited andIndex: self currentMatrixIndex andOriginTile: startTile andSet: self outputSet.
+	self fillDfsWithVisited: visited andIndex: self currentMatrixIndex andOriginTile: startTile.
 
     ^ self outputSet
 ]
 
 {
-	#category : #forms,
-	#'squeak_changestamp' : 'JS 7/11/2024 18:28'
+	#category : #brushHelper,
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:32'
 }
-GMTEBrush >> fillDfsWithVisited: aVisitedMatrix andIndex: anIndex andOriginTile: anOriginTile andSet: aSet [
-	self flag: 'REFACTOR!'.
-	
+GMTEBrush >> fillDfsWithVisited: aVisitedMatrix andIndex: anIndex andOriginTile: anOriginTile [
+
+	| newIndex newTile |
 	GMTEBrush borderingOffsets do: [:offset |
-		| newIndex newTile tilesNil tilesSame |
 		newIndex := offset + anIndex.
 		((self layer inBounds: newIndex) and: [(aVisitedMatrix at: newIndex y at: newIndex x) isNil]) ifTrue:[
 			newTile := self layer at: newIndex y at: newIndex x.
 			
-			tilesNil := (anOriginTile isNil) and: [newTile isNil].
-			tilesSame := (anOriginTile isNil not and: [newTile isNil not]) and: [anOriginTile imageForm bits hash = newTile imageForm bits hash].
-			
-			(tilesNil or: tilesSame) ifTrue: [
-					aSet add: newIndex.
+			(self tile: anOriginTile equalsTile: newTile) ifTrue: [
+					self outputSet add: newIndex.
 					aVisitedMatrix at: newIndex y at: newIndex x put: true.
-					self fillDfsWithVisited: aVisitedMatrix andIndex: newIndex andOriginTile: anOriginTile andSet: aSet]]]
+					self fillDfsWithVisited: aVisitedMatrix andIndex: newIndex andOriginTile: anOriginTile]]]
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/9/2024 08:49'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:41'
 }
 GMTEBrush >> firstMatrixIndex [
+
 	^ firstMatrixIndex
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/9/2024 08:49'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:42'
 }
-GMTEBrush >> firstMatrixIndex: anObject [
-	firstMatrixIndex := anObject
+GMTEBrush >> firstMatrixIndex: anIndex [
+
+	firstMatrixIndex := anIndex
 ]
 
 {
-	#category : #forms,
+	#category : #initialization,
 	#'squeak_changestamp' : 'JS 7/11/2024 13:59'
 }
 GMTEBrush >> initialize [
@@ -150,34 +156,36 @@ GMTEBrush >> initialize [
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/6/2024 14:51'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:42'
 }
 GMTEBrush >> layer [
+
 	^ layer
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/6/2024 14:51'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:42'
 }
-GMTEBrush >> layer: anObject [
-	layer := anObject
+GMTEBrush >> layer: aLayer [
+
+	layer := aLayer
 ]
 
 {
-	#category : #forms,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/11/2024 17:11'
+	#category : #brushes,
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:53'
 }
 GMTEBrush >> lineBrush [
 
 	self resetOutputSet.
-	self firstMatrixIndex ifNil: [^nil].
+	self firstMatrixIndex ifNil: [^ nil].
 
-	(self rasterizeLineBetweenAStart: self firstMatrixIndex andAnEnd: self currentMatrixIndex) do: [:point |
+	(self rasterizeLineBetweenStart: self firstMatrixIndex andEnd: self currentMatrixIndex) do: [:index |
 		(self calculateOffsetsForRadius: self offsetCorrectedRadius) do: [:offset | 
-			self outputSet add: (point + offset)]].
+			self outputSet add: (index + offset)]].
 
-	^(self outputSet)
+	^ self outputSet
 
 ]
 
@@ -193,18 +201,20 @@ GMTEBrush >> offsetCorrectedRadius [
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/9/2024 21:18'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:43'
 }
 GMTEBrush >> outputSet [
+
 	^ outputSet
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/9/2024 21:18'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:43'
 }
-GMTEBrush >> outputSet: anObject [
-	outputSet := anObject
+GMTEBrush >> outputSet: aSet [
+
+	outputSet := aSet
 ]
 
 {
@@ -218,15 +228,15 @@ GMTEBrush >> radius [
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/11/2024 17:15'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:43'
 }
-GMTEBrush >> radius: aNumber [
+GMTEBrush >> radius: aRadius [
 
-	radius := aNumber
+	radius := aRadius
 ]
 
 {
-	#category : #forms,
+	#category : #brushes,
 	#'squeak_changestamp' : 'Valentin Teutschbein 7/11/2024 17:09'
 }
 GMTEBrush >> radiusBrush [
@@ -239,62 +249,64 @@ GMTEBrush >> radiusBrush [
 ]
 
 {
-	#category : #forms,
-	#'squeak_changestamp' : 'JS 7/11/2024 18:26'
+	#category : #brushHelper,
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:52'
 }
-GMTEBrush >> rasterizeLineBetweenAStart: aStartPoint andAnEnd: anEndPoint [
+GMTEBrush >> rasterizeLineBetweenStart: aStartIndex andEnd: anEndIndex [
 	"implementation of Bresenhams Line Algorithm"
 	
-	| linePointsCollection deltaX deltaY stepX stepY error error2 x y |
+	| lineIndexCollection deltaX deltaY stepX stepY error error2 x y index |
 	
-	self flag: 'todo: method extraction? - Ich glaube geht schlecht'.
+	self flag: 'repeat formatting'.
 	
-    	deltaX := (anEndPoint x - aStartPoint x) abs.
-    	deltaY := (anEndPoint y - aStartPoint y) abs.
-    	stepX := (aStartPoint x < anEndPoint x) ifTrue: [1] ifFalse: [-1].
-    	stepY := (aStartPoint y < anEndPoint y) ifTrue: [1] ifFalse: [-1].
+    	deltaX := (anEndIndex x - aStartIndex x) abs.
+    	deltaY := (anEndIndex y - aStartIndex y) abs.
+    	stepX := (aStartIndex x < anEndIndex x) ifTrue: [1] ifFalse: [-1].
+    	stepY := (aStartIndex y < anEndIndex y) ifTrue: [1] ifFalse: [-1].
     	error := deltaX - deltaY.
-    	x := aStartPoint x.
-    	y := aStartPoint y.
+    	x := aStartIndex x.
+    	y := aStartIndex y.
 
-    	linePointsCollection := OrderedCollection new.
+    	lineIndexCollection := OrderedCollection new.
 
-    	[
-        	| point |
-        	point := x @ y.
-		linePointsCollection add: point.
-        	(x = anEndPoint x and: [y = anEndPoint y]) ifTrue: [
-			^linePointsCollection].
+    	[	index := x @ y.
+		lineIndexCollection add: index.
+        	(x = anEndIndex x and: [y = anEndIndex y]) ifTrue: [^ lineIndexCollection].
         	error2 := 2 * error.
         	(error2 > (0 - deltaY)) ifTrue: [
             	error := error - deltaY.
             	x := x + stepX].
         	(error2 < deltaX) ifTrue: [
             	error := error + deltaX.
-            	y := y + stepY]
-    	] repeat
+            	y := y + stepY]] repeat
 
 ]
 
 {
-	#category : #forms,
-	#'squeak_changestamp' : 'JS 7/11/2024 17:34'
+	#category : #brushes,
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:57'
 }
 GMTEBrush >> rectangleBrush [
 
+	| endCol endRow startCol startRow |
 	self resetOutputSet.
     	self firstMatrixIndex ifNil: [^ nil].
 
-    	(self currentMatrixIndex x min: self firstMatrixIndex x) to: (self currentMatrixIndex x max: self firstMatrixIndex x) do: [:row |
-        	(self currentMatrixIndex y min: self firstMatrixIndex y) to: (self currentMatrixIndex y max: self firstMatrixIndex y) do: [:col | 
-			self outputSet add: (row @ col)]].
+	startRow := (self currentMatrixIndex x min: self firstMatrixIndex x).
+	endRow := (self currentMatrixIndex x max: self firstMatrixIndex x).
+	startCol := (self currentMatrixIndex y min: self firstMatrixIndex y).
+	endCol := (self currentMatrixIndex y max: self firstMatrixIndex y).
+
+	startRow to: endRow do: [:row |
+ 		startCol to: endCol do: [:col |
+			self outputSet add: (row@col)]].
 
     ^ self outputSet
 
 ]
 
 {
-	#category : #select,
+	#category : #brushHelper,
 	#'squeak_changestamp' : 'JS 7/11/2024 13:43'
 }
 GMTEBrush >> resetOutputSet [
@@ -337,3 +349,16 @@ GMTEBrush >> selectRectangleBrush [
 
 	self currentBrush: [self rectangleBrush]
 ]
+
+{
+	#category : #brushHelper,
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 13:31'
+}
+GMTEBrush >> tile: aTile equalsTile: anotherTile [
+	
+	| tilesNil tilesSame |
+	tilesNil := (aTile isNil) and: [anotherTile isNil].
+	tilesSame := (aTile isNil not and: [anotherTile isNil not]) and: [aTile imageForm bits hash = anotherTile imageForm bits hash].
+	
+	^ (tilesNil or: [tilesSame])
+]
diff --git a/source/GM-TE/GMTEEditorTileMap.class.st b/source/GM-TE/GMTEEditorTileMap.class.st
index 5de7b5f5..dcc54e73 100644
--- a/source/GM-TE/GMTEEditorTileMap.class.st
+++ b/source/GM-TE/GMTEEditorTileMap.class.st
@@ -22,59 +22,37 @@ GMTEEditorTileMap class >> tileWidth: aWidth tileHeight: aHeight padding: aPaddi
 		model: aModel
 ]
 
-{
-	#category : #TODO,
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/5/2024 17:07'
-}
-GMTEEditorTileMap >> calculateTileCollectionFromPosition: aPos andLayer: aLayer [
-
-	| index rawCollection resultCollection |
-	self flag: 'remove method'.
-	index := self tileIndexFromPosition: aPos.
-	index ifNil: [^ nil].
-	rawCollection := OrderedCollection new.
-	resultCollection := OrderedCollection new.
-	self flag: 'Add different algos'.
-	rawCollection add: (self tileMatrixStack layer: aLayer at: index y at: index x).
-	self halt.
-
-	rawCollection add: (self tileMatrixStack layer: aLayer at: index y at: ((index x)+1)).
-	rawCollection do: [:t |
-		t ifNil: [resultCollection add: (self generateTileAtlayer: aLayer x: index x y: index y stack: self tileMatrixStack tileType: GMTETile)].
-		t ifNotNil: [resultCollection add: t]
-	].
-	^ resultCollection
-]
-
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Alex M 6/28/2024 19:28'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:15'
 }
 GMTEEditorTileMap >> currentTileChanges [
+
 	^ currentTileChanges
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Alex M 6/28/2024 19:28'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:18'
 }
-GMTEEditorTileMap >> currentTileChanges: anObject [
-	currentTileChanges := anObject
+GMTEEditorTileMap >> currentTileChanges: aTileDictionary [
+
+	currentTileChanges := aTileDictionary
 ]
 
 {
 	#category : #updating,
-	#'squeak_changestamp' : 'JS 7/12/2024 11:30'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:21'
 }
-GMTEEditorTileMap >> deleteTiles: aCoordinateCollection inLayer: aLayer [
+GMTEEditorTileMap >> deleteTiles: anIndexSet inLayer: aLayer [
 	"delete tiles from editable matrix stack at given indices"
 	
 	| tile |
-	aCoordinateCollection do: [:c |
+	anIndexSet do: [:c |
 		((self tileMatrixStack layer: aLayer) inBounds: c) ifTrue: [
 			tile := self tileMatrixStack layer: aLayer at: c y at: c x.
 			tile	ifNotNil: [ 
-				self savePreviousImageFromMatrixCoordinate: c inLayer: aLayer.
+				self savePreviousImageFromIndex: c inLayer: aLayer.
 				tile abandon.
 				self tileMatrixStack layer: aLayer at: c y at: c x put: nil.
 				self saveNewImageFromPosition: tile position inLayer: aLayer]]].
@@ -210,14 +188,14 @@ GMTEEditorTileMap >> mouseUp: anEvent [
 
 {
 	#category : #updating,
-	#'squeak_changestamp' : 'JS 7/12/2024 11:30'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:21'
 }
 GMTEEditorTileMap >> placeTiles: aCoordinateCollection inLayer: aLayer [
 	"Add currently selected tile (model) to editable matrix stack at given indices"
 	
 	| tile |
 	aCoordinateCollection do: [:c |
-		self savePreviousImageFromMatrixCoordinate: c inLayer: aLayer.
+		self savePreviousImageFromIndex: c inLayer: aLayer.
 		((self tileMatrixStack layer: aLayer) inBounds: c) ifTrue: [
 				tile := self tileMatrixStack layer: aLayer at: c y at: c x.
 				tile ifNil: [ tile := self generateTileAtlayer: aLayer x: c x y: c y stack: tileMatrixStack tileType: GMTETile].
@@ -228,18 +206,20 @@ GMTEEditorTileMap >> placeTiles: aCoordinateCollection inLayer: aLayer [
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Alex M 6/28/2024 19:44'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:16'
 }
 GMTEEditorTileMap >> previousTileStates [
+
 	^ previousTileStates
 ]
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'Alex M 6/28/2024 19:44'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:18'
 }
-GMTEEditorTileMap >> previousTileStates: anObject [
-	previousTileStates := anObject
+GMTEEditorTileMap >> previousTileStates: aTileDictionary [
+
+	previousTileStates := aTileDictionary
 ]
 
 {
@@ -282,9 +262,9 @@ GMTEEditorTileMap >> resetTileEditChanges [
 
 {
 	#category : #'command processing',
-	#'squeak_changestamp' : 'Alex M 7/6/2024 01:31'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:20'
 }
-GMTEEditorTileMap >> saveNewImageFromCoordinate: aCoordinate inLayer: aLayer [
+GMTEEditorTileMap >> saveNewImageFromIndex: aCoordinate inLayer: aLayer [
 	| tile | 
 	
 	tile := self tileMatrixStack layer: aLayer at: aCoordinate y at: aCoordinate x.
@@ -296,18 +276,18 @@ GMTEEditorTileMap >> saveNewImageFromCoordinate: aCoordinate inLayer: aLayer [
 
 {
 	#category : #'command processing',
-	#'squeak_changestamp' : 'Alex M 7/6/2024 01:34'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:20'
 }
 GMTEEditorTileMap >> saveNewImageFromPosition: aPosition inLayer: aLayer [
 	
-	self saveNewImageFromCoordinate: (self tileIndexFromPosition: aPosition) inLayer: aLayer
+	self saveNewImageFromIndex: (self tileIndexFromPosition: aPosition) inLayer: aLayer
 ]
 
 {
 	#category : #'command processing',
-	#'squeak_changestamp' : 'Alex M 7/6/2024 01:54'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:20'
 }
-GMTEEditorTileMap >> savePreviousImageFromCoordinate: aCoordinate inLayer: aLayer [
+GMTEEditorTileMap >> savePreviousImageFromIndex: aCoordinate inLayer: aLayer [
 	| tile | 
 	
 	tile := self tileMatrixStack layer: aLayer at: aCoordinate y at: aCoordinate x.
@@ -319,25 +299,11 @@ GMTEEditorTileMap >> savePreviousImageFromCoordinate: aCoordinate inLayer: aLaye
 
 {
 	#category : #'command processing',
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/6/2024 11:46'
-}
-GMTEEditorTileMap >> savePreviousImageFromMatrixCoordinate: aCoordinate inLayer: aLayer [
-	| tile |
-	
-	tile := self tileMatrixStack layer: aLayer at: aCoordinate y at: aCoordinate x.
-	
-	tile
-		ifNil: [self previousTileStates at: {aCoordinate x. aCoordinate y. aLayer} ifAbsentPut: nil]
-		ifNotNil: [self previousTileStates at: {aCoordinate x. aCoordinate y. aLayer} ifAbsentPut: tile fullResolutionSprite]
-]
-
-{
-	#category : #'command processing',
-	#'squeak_changestamp' : 'Valentin Teutschbein 7/6/2024 11:58'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:20'
 }
 GMTEEditorTileMap >> savePreviousImageFromPosition: aPosition inLayer: aLayer [
 	
-	self savePreviousImageFromCoordinate: (self tileIndexFromPosition: aPosition) inLayer: aLayer
+	self savePreviousImageFromIndex: (self tileIndexFromPosition: aPosition) inLayer: aLayer
 ]
 
 {
@@ -362,11 +328,11 @@ GMTEEditorTileMap >> tileSelectionSet [
 
 {
 	#category : #accessing,
-	#'squeak_changestamp' : 'TW 6/22/2024 01:25'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:16'
 }
-GMTEEditorTileMap >> tileSelectionSet: anObject [
+GMTEEditorTileMap >> tileSelectionSet: aSet [
 
-	tileSelectionSet := anObject
+	tileSelectionSet := aSet
 ]
 
 {
@@ -381,14 +347,14 @@ GMTEEditorTileMap >> updateTileSprite: aTile [
 
 {
 	#category : #updating,
-	#'squeak_changestamp' : 'JS 7/12/2024 11:31'
+	#'squeak_changestamp' : 'Valentin Teutschbein 7/12/2024 14:13'
 }
-GMTEEditorTileMap >> updateTiles: aCoordinateCollection inLayer: aLayer FromEvent: anEvent [
+GMTEEditorTileMap >> updateTiles: anIndexSet inLayer: aLayer FromEvent: anEvent [
 	
 	(self tileIndexFromPosition: anEvent position) ifNil: [^ nil].
 	
-	(anEvent redButtonChanged and: [self model selectedTile notNil]) ifTrue: [self placeTiles: aCoordinateCollection inLayer: aLayer].	
-	(anEvent yellowButtonChanged) ifTrue: [self deleteTiles: aCoordinateCollection inLayer: aLayer].
+	(anEvent redButtonChanged and: [self model selectedTile notNil]) ifTrue: [self placeTiles: anIndexSet inLayer: aLayer].	
+	(anEvent yellowButtonChanged) ifTrue: [self deleteTiles: anIndexSet inLayer: aLayer].
 	
 	self model savedSinceModified: false
 ]