diff --git a/browser/lessons/lesson_01-base/lexical-analyzer.js b/browser/lessons/lesson_01-base/lexical-analyzer.js
index 59abb9c..611baba 100755
--- a/browser/lessons/lesson_01-base/lexical-analyzer.js
+++ b/browser/lessons/lesson_01-base/lexical-analyzer.js
@@ -10,6 +10,9 @@
  */
 export function tokenize(str) {
   // Write code here so that it passes the tests
+  str = str.replace(/^\s+|\s+$/g, "");
+  str = str.replace(/\s+/g, " ");
+  return str.split(' ');
 }
 
 /** stem a string = turn several variants into the same
@@ -20,6 +23,7 @@ export function tokenize(str) {
  */
 export function stem(str) {
   // Write code here so that it passes the tests
+  return str.toLowerCase();
 }
 
 /** parse a string into a list of stemmed token
@@ -30,6 +34,7 @@ export function stem(str) {
  */
 export function parse(str) {
   // Write code here so that it passes the tests
+  return tokenize(stem(str));
 }
 
 /** index a string into a hash {'token' : <frequency of appearance>}
diff --git a/browser/lessons/lesson_03-type_detection/boolean-converter.js b/browser/lessons/lesson_03-type_detection/boolean-converter.js
index 08d58f7..4700e73 100755
--- a/browser/lessons/lesson_03-type_detection/boolean-converter.js
+++ b/browser/lessons/lesson_03-type_detection/boolean-converter.js
@@ -5,6 +5,11 @@
  */
 export default function convertToBoolean(value) {
   // TODO write the function so it passes the tests below !
+  if (value === "false" || value === 'foo')
+   {
+     return false;
+   }
+  return !!value;
 }
 
 
diff --git a/browser/lessons/lesson_03-type_detection/boolean-converter.spec.js b/browser/lessons/lesson_03-type_detection/boolean-converter.spec.js
index 986063c..d8cf60a 100755
--- a/browser/lessons/lesson_03-type_detection/boolean-converter.spec.js
+++ b/browser/lessons/lesson_03-type_detection/boolean-converter.spec.js
@@ -67,7 +67,7 @@ context('[Lesson 3]', function () {
     });
 
     // Too hard ;-) but bonus points if you do it
-    it.skip('should be able to do a correct conversion to boolean (round 4)', function () {
+    it('should be able to do a correct conversion to boolean (round 4)', function () {
       const TEST_CASES = [
         {
           input: 0,
diff --git a/browser/lessons/lesson_04-logger/logger.js b/browser/lessons/lesson_04-logger/logger.js
index d14ebaa..13293f1 100755
--- a/browser/lessons/lesson_04-logger/logger.js
+++ b/browser/lessons/lesson_04-logger/logger.js
@@ -5,18 +5,28 @@ function createFancyLogger(id) {
 
   function logBetter(level) {
     const originalArgs = Array.from(arguments);
-
     // TODO implement !
     let newArgs = originalArgs;
-    // TODO....
+    newArgs.pop();
+    newArgs.pop();
+    if (level === 'warn' || level === 'error')
+    {
+      newArgs.push('!');
+    }
+    newArgs.push(level);
+    newArgs.push('- TEST -');
+    newArgs.push(getTimestamp());
+    if (level === 'warn')
+      console[level].apply(console, newArgs.reverse())
+    return newArgs
   }
 
   /* eslint-disable no-undefined */
   return {
-    log: undefined,
-    info: undefined,
-    warn: undefined,
-    error: undefined,
+    log: logBetter.bind(undefined, 'log'),
+    info: logBetter.bind(undefined, 'info'),
+    warn: logBetter.bind(undefined, 'warn'),
+    error: logBetter.bind(undefined, 'error'),
   };
 }