diff --git a/hw3/Claudio_Maggioni/scripts/app.js b/hw3/Claudio_Maggioni/scripts/app.js
index 087f490..b0a499f 100644
--- a/hw3/Claudio_Maggioni/scripts/app.js
+++ b/hw3/Claudio_Maggioni/scripts/app.js
@@ -1,5 +1,13 @@
 // vim: set ts=2 sw=2 et tw=80:
 class App {
+  static get BRUSHES() {
+    return {
+      "PenBrush": new PenBrush(),
+      "DiscBrush": new DiscBrush(),
+      "StarBrush": new StarBrush(),
+    };
+  }
+
   constructor(conf) {
     if (!(typeof conf === 'object' && conf)) {
       throw new Error('Argument conf different from specification');
@@ -15,12 +23,17 @@ class App {
 
     if (typeof conf.buttons === 'object' && conf.buttons) {
       this.buttons = {}
-      for (const b of ['clear', 'button', 'camera'])
+      for (const b of ['clear', 'undo', 'camera'])
         this.buttons[b] = document.getElementById(conf.buttons[b]);
 
       if (this.buttons.clear)
-        this.buttons.clear.addEventListener('click', () =>
-          this.ctx.clearRect(0, 0, canvas.width, canvas.height));
+        this.buttons.clear.addEventListener('click', () => {
+          this.erase();
+          history.clear();
+        });
+
+      if (this.buttons.undo)
+        this.buttons.undo.addEventListener('click', () => history.pop(this));
 
       if (this.buttons.camera)
         this.buttons.camera.addEventListener('click', () => {
@@ -34,29 +47,22 @@ class App {
         });
     }
 
-    this.canvas.addEventListener('mousedown', (e) => {
-      this.ctx.save();
-      this.ctx.lineWidth = 1;
-      this.ctx.moveTo(e.offsetX, e.offsetY);
-      this.ctx.beginPath();
-      this.mousedown = true;
-    });
-
-    this.canvas.addEventListener('mousemove', (e) => this.mousedown && this.draw(e));
-
-    const endPath = (e) => {
-      if (this.mousedown) {
-        this.ctx.lineTo(e.offsetX, e.offsetY);
-        this.ctx.stroke();
-        this.ctx.restore();
-        this.mousedown = false;
-      }
-    };
-
-    this.canvas.addEventListener('mouseup', endPath);
-    this.canvas.addEventListener('mouseout', endPath);
-
+    this.ctx.lineWidth = 1;
     this.strokeStyle = this.constructor.defaultStrokeStyle;
+    this.brush = "PenBrush";
+
+    const brushToolbar = document.querySelector('#brush-toolbar');
+    for (const name in App.BRUSHES) {
+      const b = document.createElement('button');
+      b.innerText = name;
+      b.addEventListener('click', () => this.brush = name);
+      brushToolbar.appendChild(b);
+    }
+
+    this.canvas.addEventListener('mousedown', this.startPath.bind(this));
+    this.canvas.addEventListener('mousemove', this.draw.bind(this));
+    this.canvas.addEventListener('mouseup', this.endPath.bind(this));
+    this.canvas.addEventListener('mouseout', this.endPath.bind(this));
   }
 
   static get defaultStrokeStyle() {
@@ -74,12 +80,63 @@ class App {
     this.ctx.strokeStyle = style;
   }
 
-  draw(e) {
-    console.log(e);
-    this.ctx.lineTo(e.offsetX, e.offsetY);
-    this.ctx.stroke();
+  get brush() {
+    return this._brush.name;
+  }
+
+  set brush(brushName) {
+    this._brush = App.BRUSHES[brushName];
+  }
+
+  erase() {
+    this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
+  }
+
+  startPath(e, record = true) {
     this.ctx.beginPath();
     this.ctx.moveTo(e.offsetX, e.offsetY);
+
+    if (record) {
+      history.initializeNewPath();
+      history.push(new Stroke(this.brush, e.offsetX, e.offsetY));
+    }
+
+    this.mousedown = true;
+  }
+
+  draw(e, beginNew = true, record = true) {
+    if (this.mousedown) {
+      this._brush.draw(this.ctx, this.strokeStyle, e.offsetX, e.offsetY);
+
+      if (record) {
+        history.push(new Stroke(this.brush, e.offsetX, e.offsetY));
+      }
+
+      if (beginNew) {
+        this.ctx.beginPath();
+        this.ctx.moveTo(e.offsetX, e.offsetY);
+      } else {
+        this.mousedown = false;
+      }
+    }
+  }
+
+  endPath(e, record = true) {
+    this.draw(e, false, record);
+  }
+
+  drawPath(path) {
+    const last = path.length - 1;
+    const lastBrush = this.brush;
+    for (let i = 0; i <= last; i++) {
+      this.brush = path[i].brushName;
+      switch(i) {
+        case 0:    this.startPath(path[i], false); break;
+        case last: this.endPath(path[i], false); break;
+        default:   this.draw(path[i], true, false);
+      }
+    }
+    this.brush = lastBrush;
   }
 }
 
diff --git a/hw3/Claudio_Maggioni/scripts/brushes.js b/hw3/Claudio_Maggioni/scripts/brushes.js
index 54e7b95..0b314ba 100644
--- a/hw3/Claudio_Maggioni/scripts/brushes.js
+++ b/hw3/Claudio_Maggioni/scripts/brushes.js
@@ -1,19 +1,53 @@
+// vim: set ts=2 sw=2 et tw=80:
+
 class PenBrush {
+  constructor() {
+    this.opacity = 1;
+    this.name = "PenBrush";
+  }
 
-    constructor() {
-        this.opacity = 1;
-        this.name = "PenBrush";
-    }
-
-    draw(ctx, strokeStyle, x, y) {
-        ctx.lineJoin = ctx.lineCap = 'round';
-        ctx.strokeStyle = strokeStyle;
-        ctx.lineTo(x, y);
-        ctx.stroke();
-    }
-
+  draw(ctx, strokeStyle, x, y) {
+    ctx.lineJoin = ctx.lineCap = 'round';
+    ctx.strokeStyle = strokeStyle;
+    ctx.lineTo(x, y);
+    ctx.stroke();
+  }
 }
 
-//TODO DiscBrush
-//TODO StarBrush
+class DiscBrush extends PenBrush {
+  static get RADIUS() { return 10; }
 
+  constructor() {
+    super();
+    this.name = "DiscBrush";
+  }
+
+  draw(ctx, strokeStyle, x, y) {
+    ctx.beginPath(); // clear previous path starting
+    ctx.ellipse(x, y, 10, 10, 0, 0, 2 * Math.PI);
+    ctx.fill();
+    ctx.stroke();
+  }
+}
+
+class StarBrush extends PenBrush {
+  constructor() {
+    super();
+    this.name = "StarBrush";
+  }
+
+  draw(ctx, strokeStyle, x, y) {
+    ctx.moveTo(x - 8, y - 3);
+    ctx.lineTo(x - 3, y - 3);
+    ctx.lineTo(x, y - 8);
+    ctx.lineTo(x + 3, y - 3);
+    ctx.lineTo(x + 8, y - 3);
+    ctx.lineTo(x + 4, y + 1);
+    ctx.lineTo(x + 4, y + 6);
+    ctx.lineTo(x, y + 3);
+    ctx.lineTo(x - 4, y + 6);
+    ctx.lineTo(x - 4, y + 1);
+    ctx.lineTo(x - 8, y - 3);
+    ctx.stroke();
+  }
+}
diff --git a/hw3/Claudio_Maggioni/scripts/undo.js b/hw3/Claudio_Maggioni/scripts/undo.js
index 7faa747..ba2f0ba 100644
--- a/hw3/Claudio_Maggioni/scripts/undo.js
+++ b/hw3/Claudio_Maggioni/scripts/undo.js
@@ -1,4 +1,39 @@
+// vim: set ts=2 sw=2 et tw=80:
+
 const history = {
+  paths: []
+}
 
-    }
+history.pop = (app) => {
+  if (history.paths.length == 0) return;
+  history.paths.pop();
+  app.erase();
+  for (const path of history.paths) {
+    app.drawPath(path);
+  }
+};
 
+history.initializeNewPath = () => {
+  history.paths.push([]);
+};
+
+history.push = (stroke) => {
+  if (!stroke instanceof Stroke) {
+    throw new Error(JSON.stringify(stroke) + ' is not a Stroke instance');
+  }
+  history.paths[history.paths.length - 1].push(stroke);
+}
+
+history.clear = () => {
+  history.paths = [];
+};
+
+
+
+class Stroke {
+  constructor(brushName, x, y) {
+    this.brushName = brushName;
+    this.offsetX = x;
+    this.offsetY = y;
+  }
+}