diff --git a/demo/app.scss b/demo/app.scss
index 32161680..e4069162 100644
--- a/demo/app.scss
+++ b/demo/app.scss
@@ -1,3 +1,5 @@
+$navbar-height: 40px;
+$main-color: #875A7B;
 
 html {
     height: 100%;
@@ -6,26 +8,27 @@ html {
 body {
     height: 100%;
     margin: 0;
-    font-family: sans-serif;
 }
 
 /* Web Client */
 .o_web_client {
+    font-family: sans-serif;
     height: 100%;
     display: grid;
-    grid-template-rows: 40px auto;
+    grid-template-rows: $navbar-height auto;
 }
 
 /* Navbar */
 .o_navbar {
-    background-color: #875A7B;
+    background-color: $main-color;
     color: white;
     display: flex;
+    line-height: $navbar-height;
 
     span.title {
-        font-size: 22px;
+        font-size: 24px;
         font-weight: bold;
-        padding: 8px;
+        padding: 0 16px;
     }
 
     ul {
@@ -36,13 +39,18 @@ body {
     }
 
     li {
-        padding: 8px 12px;
+        margin: 0 4px;
         font-size: 20px;
+        &:hover {
+            background-color: darken($main-color, 10);
+        }
     }
 
     a {
         color: white;
         text-decoration: none;
+        padding: 0 5px;
+
     }
 }
 
diff --git a/demo/src/Navbar.ts b/demo/src/Navbar.ts
deleted file mode 100644
index f6fc2a7d..00000000
--- a/demo/src/Navbar.ts
+++ /dev/null
@@ -1,20 +0,0 @@
-import Widget from "../../src/core/widget";
-
-const template = `
-    <div class="o_navbar">
-        <span class="title">Odoo</span>
-        <ul>
-            <li t-foreach="state.items" t-as="item">
-                <a href="someaction"><t t-esc="item.title"/></a>
-            </li>
-        </ul>
-    </div>
-`;
-
-export default class Navbar extends Widget {
-  name = "navbar";
-  template = template;
-  state = {
-    items: [{title: 'Discuss'}, {title: 'CRM'}]
-  };
-}
diff --git a/demo/src/RootWidget.ts b/demo/src/RootWidget.ts
deleted file mode 100644
index bc3113e8..00000000
--- a/demo/src/RootWidget.ts
+++ /dev/null
@@ -1,44 +0,0 @@
-import Widget from "../../src/core/widget";
-import Counter from "./Counter";
-import Navbar from "./Navbar";
-
-const template = `
-    <div class="o_web_client">
-        <t t-widget="Navbar"/>
-        <div class="o_content">
-            <span>Root Widget</span>
-            <button t-on-click="resetCounter">Reset</button>
-            <button t-on-click="resetCounterAsync">Reset in 3s</button>
-            <button t-on-click="toggle">Toggle  Counter</button>
-            <input/>
-            <t t-if="state.validcounter">
-                <t t-widget="Counter" t-ref="counter" t-props="{initialState:4}"/>
-            </t>
-            <t t-else="1">
-                <t t-widget="Counter" t-ref="counter" t-props="{initialState:7}"/>
-            </t>
-            <div ref="target"/>
-        </div>
-    </div>
-`;
-
-export default class RootWidget extends Widget {
-  name = "root";
-  template = template;
-  widgets = { Counter, Navbar };
-  state = { validcounter: true};
-
-  resetCounter(ev: MouseEvent) {
-      this.refs.counter.updateState({counter: 3})
-  }
-
-  resetCounterAsync(ev: MouseEvent) {
-      setTimeout(() => {
-          this.refs.counter.updateState({counter: 3})
-      }, 3000);
-  }
-
-  toggle() {
-      this.updateState({validcounter: !this.state.validcounter});
-  }
-}
diff --git a/demo/src/env.ts b/demo/src/env.ts
index ebbf8e16..c579ec0f 100644
--- a/demo/src/env.ts
+++ b/demo/src/env.ts
@@ -1,11 +1,14 @@
 import { Env } from "../../src/core/widget";
 import QWeb from "../../src/core/qweb_vdom";
+import Router from "./services/router";
+import actions from "./services/actions";
 
 const qweb = new QWeb();
+const router = new Router();
 
 const env: Env = {
   qweb: qweb,
-  services: {}
+  services: { router, actions }
 };
 
 export default env;
diff --git a/demo/src/main.ts b/demo/src/main.ts
index 46598977..46daa996 100644
--- a/demo/src/main.ts
+++ b/demo/src/main.ts
@@ -1,10 +1,9 @@
 ///<amd-module name="main" />
 
-import RootWidget from "./RootWidget";
+import RootWidget from "./widgets/RootWidget";
 import env from "./env";
 
 document.addEventListener("DOMContentLoaded", async function() {
-  const rootWidget = new RootWidget(null);
-  rootWidget.setEnvironment(env);
+  const rootWidget = new RootWidget(env);
   await rootWidget.mount(document.body);
 });
diff --git a/demo/src/services/actions.ts b/demo/src/services/actions.ts
new file mode 100644
index 00000000..8ad5248a
--- /dev/null
+++ b/demo/src/services/actions.ts
@@ -0,0 +1,17 @@
+import CRM from "../widgets/CRM";
+import Discuss from "../widgets/Discuss";
+import Widget from "../../../src/core/widget";
+
+export interface Action {
+  id: number;
+  title: string;
+  Widget: typeof Widget;
+  default?: boolean;
+}
+
+const actions: Action[] = [
+  { id: 1, title: "Discuss", Widget: Discuss, default: true },
+  { id: 2, title: "CRM", Widget: CRM }
+];
+
+export default actions;
diff --git a/demo/src/services/router.ts b/demo/src/services/router.ts
new file mode 100644
index 00000000..b8c4d71e
--- /dev/null
+++ b/demo/src/services/router.ts
@@ -0,0 +1,64 @@
+export type Route = string;
+export type Query = { [key: string]: string };
+
+export interface RouteInfo {
+  route: Route;
+  query: Query;
+  title: string;
+}
+
+export default class Router {
+  listeners: { owner: any; callback: (info: RouteInfo) => void }[] = [];
+
+  constructor() {
+    window.addEventListener("popstate", this.onUrlChange.bind(this));
+  }
+
+  onUrlChange() {
+      const info = this.getRouteInfo();
+      for (let listener of this.listeners) {
+          listener.callback.call(listener.owner, info);
+      }
+  }
+
+  /**
+   * @param {Route} route relative route: for example, /web/
+   * @param {Query} query
+   */
+  navigate(info: Partial<RouteInfo>) {
+    const currentRouteInfo = this.getRouteInfo();
+    const route = info.route || currentRouteInfo.route;
+    const query = info.query || {};
+    const title = info.title || currentRouteInfo.title;
+    const url = this.formatURL(route, query);
+    window.history.pushState(null, title, url);
+  }
+  register(owner: any, callback: (info: RouteInfo) => void) {
+    this.listeners.push({ owner, callback });
+  }
+
+  unregister(owner: any) {
+    this.listeners = this.listeners.filter(l => l.owner !== owner);
+  }
+
+  formatURL(route: Route, query: Query): string {
+    let url = route;
+    let hasHash = false;
+    for (let key in query) {
+      url = url + (hasHash ? "&" : "#");
+      url = url + `${key}=${query[key]}`;
+      hasHash = true;
+    }
+    return url;
+  }
+
+  getRouteInfo(): RouteInfo {
+    const route = window.location.pathname.slice(1);
+    const query = {};
+    for (let part of window.location.hash.slice(1).split("?")) {
+      let [key, value] = part.split("=");
+      query[key] = value;
+    }
+    return { route, query, title: document.title };
+  }
+}
diff --git a/demo/src/widgets/CRM.ts b/demo/src/widgets/CRM.ts
new file mode 100644
index 00000000..5ccff573
--- /dev/null
+++ b/demo/src/widgets/CRM.ts
@@ -0,0 +1,12 @@
+import Widget from "../../../src/core/widget";
+
+const template = `
+    <div class="o_crm">
+        <span>CRM!!!!</span>
+    </div>
+`;
+
+export default class Discuss extends Widget {
+  name = "crm";
+  template = template;
+}
diff --git a/demo/src/Counter.ts b/demo/src/widgets/Counter.ts
similarity index 92%
rename from demo/src/Counter.ts
rename to demo/src/widgets/Counter.ts
index 656c6da9..094b8e58 100644
--- a/demo/src/Counter.ts
+++ b/demo/src/widgets/Counter.ts
@@ -1,4 +1,4 @@
-import Widget from "../../src/core/widget";
+import Widget from "../../../src/core/widget";
 
 const template = `
     <div>
diff --git a/demo/src/widgets/Discuss.ts b/demo/src/widgets/Discuss.ts
new file mode 100644
index 00000000..7c2e3c79
--- /dev/null
+++ b/demo/src/widgets/Discuss.ts
@@ -0,0 +1,40 @@
+import Widget from "../../../src/core/widget";
+import Counter from "./Counter";
+
+const template = `
+    <div class="o_discuss">
+        <span>Root Widget</span>
+        <button t-on-click="resetCounter">Reset</button>
+        <button t-on-click="resetCounterAsync">Reset in 3s</button>
+        <button t-on-click="toggle">Toggle  Counter</button>
+        <input/>
+        <t t-if="state.validcounter">
+            <t t-widget="Counter" t-ref="counter" t-props="{initialState:4}"/>
+        </t>
+        <t t-else="1">
+            <t t-widget="Counter" t-ref="counter" t-props="{initialState:7}"/>
+        </t>
+        <div ref="target"/>
+    </div>
+`;
+
+export default class Discuss extends Widget {
+  name = "discuss";
+  template = template;
+  widgets = { Counter };
+  state = { validcounter: true };
+
+  resetCounter(ev: MouseEvent) {
+    this.refs.counter.updateState({ counter: 3 });
+  }
+
+  resetCounterAsync(ev: MouseEvent) {
+    setTimeout(() => {
+      this.refs.counter.updateState({ counter: 3 });
+    }, 3000);
+  }
+
+  toggle() {
+    this.updateState({ validcounter: !this.state.validcounter });
+  }
+}
diff --git a/demo/src/widgets/Navbar.ts b/demo/src/widgets/Navbar.ts
new file mode 100644
index 00000000..099913ed
--- /dev/null
+++ b/demo/src/widgets/Navbar.ts
@@ -0,0 +1,23 @@
+import Widget from "../../../src/core/widget";
+import { Action } from "../services/actions";
+
+const template = `
+    <div class="o_navbar">
+        <span class="title">Odoo</span>
+        <ul>
+            <li t-foreach="env.services.actions" t-as="action">
+                <a t-att-href="getUrl(action)"><t t-esc="action.title"/></a>
+            </li>
+        </ul>
+    </div>
+`;
+
+export default class Navbar extends Widget {
+  name = "navbar";
+  template = template;
+
+  getUrl(action: Action) {
+    const action_id = action.id;
+    return this.env.services.router.formatURL("web", { action_id });
+  }
+}
diff --git a/demo/src/widgets/RootWidget.ts b/demo/src/widgets/RootWidget.ts
new file mode 100644
index 00000000..82f579a3
--- /dev/null
+++ b/demo/src/widgets/RootWidget.ts
@@ -0,0 +1,54 @@
+import Widget, { Env } from "../../../src/core/widget";
+import Navbar from "./Navbar";
+import { Action } from "../services/actions";
+
+const template = `
+    <div class="o_web_client">
+        <t t-widget="Navbar"/>
+        <div class="o_content">
+          <t t-widget="Content"/>
+        </div>
+    </div>
+`;
+
+export default class RootWidget extends Widget {
+  name = "root";
+  template = template;
+  widgets = { Navbar };
+  state = { validcounter: true };
+
+  constructor(env: Env) {
+    super(env);
+    this.setMainWidget();
+  }
+
+  mounted() {
+    this.env.services.router.register(this, this.onUrlChange);
+  }
+
+  setMainWidget() {
+    const action = this.getAction();
+    (<any>this.widgets).Content = action.Widget;
+  }
+
+  onUrlChange() {
+    this.setMainWidget();
+    // notice that this can only be safely done because the root widget is
+    // mounted now.
+    this.render();
+  }
+
+  getAction(): Action {
+    const routeInfo = this.env.services.router.getRouteInfo();
+    const actionID = parseInt(routeInfo.query.action_id);
+    let actions: Action[] = this.env.services.actions;
+    let action = actions.find(a => a.id === actionID);
+    if (!action) {
+      action = actions.find(a => a.default === true);
+      if (!action) {
+        throw new Error("No valid action!");
+      }
+    }
+    return action;
+  }
+}
diff --git a/package.json b/package.json
index 0345f963..cf8d6013 100644
--- a/package.json
+++ b/package.json
@@ -11,7 +11,7 @@
     "demo:build": "cp -r demo/ dist/demo && npm run demo:build:js && npm run demo:build:css",
     "demo:build:css": "sass demo/app.scss dist/demo/app.css",
     "demo:build:js": "tsc --allowjs -m amd --lib es2017,dom --target esnext --outfile dist/demo/main.js demo/src/main.ts",
-    "demo:serve": "live-server dist/demo/",
+    "demo:serve": "live-server --entry-file=index.html dist/demo/",
     "predemo:dev": "npm run demo:build",
     "demo:dev": "npm-run-all --parallel \"demo:build:* -- --watch\" demo:serve"
   },
diff --git a/src/core/widget.ts b/src/core/widget.ts
index 858ffd57..3a8aac2b 100644
--- a/src/core/widget.ts
+++ b/src/core/widget.ts
@@ -18,9 +18,9 @@ export default class Widget {
   template: string = "<div></div>";
   vnode: VNode | null = null;
 
-  parent: Widget | null;
+  parent: Widget | null = null;
   children: Widget[] = [];
-  env: Env | null = null;
+  env: Env;
   el: HTMLElement | null = null;
   state: Object = {};
   refs: { [key: string]: Widget } = {};
@@ -29,13 +29,13 @@ export default class Widget {
   // Lifecycle
   //--------------------------------------------------------------------------
 
-  constructor(parent: Widget | null, props?: any) {
-    this.parent = parent;
-    if (parent) {
+  constructor(parent: Widget | Env, props?: any) {
+    if (parent instanceof Widget) {
+      this.parent = parent;
       parent.children.push(this);
-      if (parent.env) {
-        this.setEnvironment(parent.env);
-      }
+      this.env = Object.create(parent.env);
+    } else {
+      this.env = parent;
     }
   }
 
@@ -59,7 +59,7 @@ export default class Widget {
     if (target) {
       target.appendChild(this.el!);
       if (document.body.contains(target)) {
-        this.visitSubTree(w => w.mounted())
+        this.visitSubTree(w => w.mounted());
       }
     }
     return vnode;
@@ -71,10 +71,6 @@ export default class Widget {
     }
   }
 
-  setEnvironment(env: Env) {
-    this.env = Object.create(env);
-  }
-
   /**
    * DOCSTRIGN
    *
diff --git a/tests/widget.test.ts b/tests/widget.test.ts
index be9458e8..d5d6e3e8 100644
--- a/tests/widget.test.ts
+++ b/tests/widget.test.ts
@@ -6,8 +6,7 @@ function makeWidget(W: typeof Widget): Widget {
     qweb: new QWeb(),
     services: {}
   };
-  const w = new W(null);
-  w.setEnvironment(env);
+  const w = new W(env);
   return w;
 }