diff --git a/lib/src/Engine.dart b/lib/src/Engine.dart
index 5653bb9..3319a06 100644
--- a/lib/src/Engine.dart
+++ b/lib/src/Engine.dart
@@ -1,5 +1,6 @@
 import 'dart:html' as html;
 
+import 'package:rules_of_living/src/Renderer.dart';
 import 'package:rules_of_living/src/Simulation.dart';
 
 class Engine {
@@ -37,7 +38,12 @@ class Engine {
   /// be used if no canvas was defined at engine creation and it should be
   /// rendered later.
   html.CanvasElement canvas;
+
   Simulation _simulation;
+  Map<int, bool> _lastSimulationUpdate = {};
+
+  Renderer _renderer;
+
   bool running = false;
 
   Engine() {
@@ -70,6 +76,7 @@ class Engine {
     }
   }
 
+  // TODO Should be renamed to something more intention revealing like hasReachedUpdateTimestepThreshold
   bool _shouldUpdate(int updateLag, int elapsed, int timeOut) {
     if (updateLag < _MS_PER_STEP) return false;
     if (elapsed > timeOut) throw StackOverflowError;
@@ -85,10 +92,10 @@ class Engine {
   void update() {
     if (_simulation == null) return;
 
-    Map<int, bool> simulationUpdate = _simulation.update();
-    _simulation.mergeStateChanges(simulationUpdate);
+    _lastSimulationUpdate = _simulation.update();
+    _simulation.mergeStateChanges(_lastSimulationUpdate);
 
-    if (simulationUpdate.length == 0) running = false;
+    if (_lastSimulationUpdate.length == 0) running = false;
   }
 
   /// Advances Logic One Update
@@ -107,9 +114,9 @@ class Engine {
   /// the internal engine processing. Does not do anything if no canvas is
   /// defined.
   void render([num interp]) {
-    if (canvas == null || _simulation == null) return;
+    if (canvas == null || _renderer == null) return;
 
-    _simulation.render(canvas, interp);
+    _renderer.render(canvas, _lastSimulationUpdate);
   }
 
   void set simulation(Simulation value) => _simulation = value;
diff --git a/lib/src/Renderer.dart b/lib/src/Renderer.dart
new file mode 100644
index 0000000..8dfc0e1
--- /dev/null
+++ b/lib/src/Renderer.dart
@@ -0,0 +1,40 @@
+import 'dart:html' as html;
+import 'dart:math' as math;
+
+import 'package:rules_of_living/src/Grid.dart';
+
+class Renderer {
+  bool _dirty = true;
+
+  bool _renderEdges = true;
+  bool get renderEdges => _renderEdges;
+  void set renderEdges(bool value) {
+    _renderEdges = value;
+    _dirty = true;
+  }
+
+  void render(html.CanvasElement canvas, Map<int, bool> map) {
+    // only renders if any cells changed between renders
+    if (!_dirty) return;
+
+    html.CanvasRenderingContext2D ctx = canvas.getContext('2d');
+    int brickW = (canvas.width ~/ map.width);
+    int brickH = (canvas.height ~/ map.height);
+    ctx.clearRect(0, 0, canvas.width, canvas.height);
+    for (int i = 0; i < map.length; i++) {
+      math.Point p = map.toCoordinates(i);
+
+      if (_renderEdges) {
+        ctx.setStrokeColorRgb(100, 100, 100);
+        ctx.strokeRect(p.x * brickW, p.y * brickH, brickW, brickH);
+      }
+
+      if (map[i] == true)
+        ctx.setFillColorRgb(155, 155, 255);
+      else
+        ctx.setFillColorRgb(0, 0, 0);
+      ctx.fillRect(p.x * brickW, p.y * brickH, brickW, brickH);
+    }
+    _dirty = false;
+  }
+}
diff --git a/lib/src/Simulation.dart b/lib/src/Simulation.dart
index 0955c9a..fd92338 100644
--- a/lib/src/Simulation.dart
+++ b/lib/src/Simulation.dart
@@ -1,4 +1,3 @@
-import 'dart:html' as html;
 import 'dart:math' as math;
 import 'dart:math';
 
@@ -14,12 +13,6 @@ class Simulation {
 
   RuleSet rules = GameOfLife();
 
-  bool _dirty = true;
-  bool get dirty => _dirty;
-
-  bool _renderEdges = true;
-  bool get renderEdges => _renderEdges;
-
   int _amount;
   int _dispersal;
 
@@ -36,9 +29,9 @@ class Simulation {
 
   Simulation.fromGrid(Grid<bool> map) : this.map = map;
 
+  //TODO this needs to RETURN a changeSet, just like the others do
   Grid<bool> reset([Grid<bool> map]) {
     map ??= this.map;
-    _dirty = true;
     map.setAll(0, List.filled(map.length, false));
     return map;
   }
@@ -60,8 +53,6 @@ class Simulation {
               cx + rng.nextInt(_dispersal), cy + rng.nextInt(_dispersal), true);
       if (sanityCheck > 100 && sanityCheck > i * 3) break;
     }
-
-    _dirty = true;
   }
 
   void setCellState(int x, int y, bool state) {
@@ -91,7 +82,6 @@ class Simulation {
 
   void mergeStateChanges(Map<int, bool> stateChanges) {
     stateChanges.forEach((i, el) => map[i] = el);
-    if (stateChanges.length != 0) _dirty = true;
   }
 
   Map<int, bool> calculateNextState(Grid<bool> oldState) {
@@ -125,39 +115,9 @@ class Simulation {
     return count;
   }
 
-  void render(html.CanvasElement canvas, [num interp]) {
-    // only renders if any cells changed between renders
-    if (!_dirty) return;
-
-    html.CanvasRenderingContext2D ctx = canvas.getContext('2d');
-    int brickW = (canvas.width ~/ map.width);
-    int brickH = (canvas.height ~/ map.height);
-    ctx.clearRect(0, 0, canvas.width, canvas.height);
-    for (int i = 0; i < map.length; i++) {
-      math.Point p = map.toCoordinates(i);
-      if (_renderEdges) {
-        ctx.setStrokeColorRgb(100, 100, 100);
-        ctx.strokeRect(p.x * brickW, p.y * brickH, brickW, brickH);
-      }
-
-      if (map[i] == true)
-        ctx.setFillColorRgb(155, 155, 255);
-      else
-        ctx.setFillColorRgb(0, 0, 0);
-      ctx.fillRect(p.x * brickW, p.y * brickH, brickW, brickH);
-    }
-    _dirty = false;
-  }
-
-  void set renderEdges(bool on) {
-    _renderEdges = on;
-    _dirty = true;
-  }
-
   void saveSnapshot() => _snapshot = Grid.from(map);
   Grid<bool> loadSnapshot() {
     map = Grid.from(_snapshot);
-    _dirty = true;
     return map;
   }
 }