diff --git a/javascript/chronometer.js b/javascript/chronometer.js
index 7a13496..6d540d1 100644
--- a/javascript/chronometer.js
+++ b/javascript/chronometer.js
@@ -1,39 +1,39 @@
 class Chronometer {
   constructor() {
-    // ... your code goes here
+    this.currentTime = 0;
+    this.intervalId = null;
   }
 
   start(callback) {
-    // ... your code goes here
+    this.intervalId = setInterval(() => {
+      this.currentTime++;
+      if (callback) callback();
+    }, 1000);
   }
 
   getMinutes() {
-    // ... your code goes here
+    return Math.floor(this.currentTime / 60);
   }
 
   getSeconds() {
-    // ... your code goes here
+    return this.currentTime % 60;
   }
 
   computeTwoDigitNumber(value) {
-    // ... your code goes here
+    return value.toString().padStart(2, '0');
   }
 
   stop() {
-    // ... your code goes here
+    clearInterval(this.intervalId);
   }
 
   reset() {
-    // ... your code goes here
+    this.currentTime = 0;
   }
 
   split() {
-    // ... your code goes here
+    return `${this.computeTwoDigitNumber(this.getMinutes())}:${this.computeTwoDigitNumber(this.getSeconds())}`;
   }
 }
 
-// The following is required to make unit tests work.
-/* Environment setup. Do not modify the below code. */
-if (typeof module !== 'undefined') {
-  module.exports = Chronometer;
-}
+export default Chronometer;
diff --git a/javascript/index.js b/javascript/index.js
index fb3a43a..386f81a 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -1,65 +1,50 @@
-const chronometer = new Chronometer();
-
-// get the buttons:
-const btnLeftElement = document.getElementById('btnLeft');
-const btnRightElement = document.getElementById('btnRight');
-
-// get the DOM elements that will serve us to display the time:
-const minDecElement = document.getElementById('minDec');
-const minUniElement = document.getElementById('minUni');
-const secDecElement = document.getElementById('secDec');
-const secUniElement = document.getElementById('secUni');
-const milDecElement = document.getElementById('milDec');
-const milUniElement = document.getElementById('milUni');
-const splitsElement = document.getElementById('splits');
-
-function printTime() {
-  // ... your code goes here
-}
-
-function printMinutes() {
-  // ... your code goes here
-}
-
-function printSeconds() {
-  // ... your code goes here
-}
-
-// ==> BONUS
-function printMilliseconds() {
-  // ... your code goes here
-}
-
-function printSplit() {
-  // ... your code goes here
-}
-
-function clearSplits() {
-  // ... your code goes here
-}
-
-function setStopBtn() {
-  // ... your code goes here
-}
-
-function setSplitBtn() {
-  // ... your code goes here
-}
-
-function setStartBtn() {
-  // ... your code goes here
-}
+import Chronometer from './chronometer.js';
 
-function setResetBtn() {
-  // ... your code goes here
-}
-
-// Start/Stop Button
-btnLeftElement.addEventListener('click', () => {
-  // ... your code goes here
+const chronometer = new Chronometer();
+const btnLeft = document.getElementById('btnLeft');
+const btnRight = document.getElementById('btnRight');
+const minDec = document.getElementById('minDec');
+const minUni = document.getElementById('minUni');
+const secDec = document.getElementById('secDec');
+const secUni = document.getElementById('secUni');
+const splits = document.getElementById('splits');
+
+function updateDisplay() {
+  const minutes = chronometer.computeTwoDigitNumber(chronometer.getMinutes());
+  const seconds = chronometer.computeTwoDigitNumber(chronometer.getSeconds());
+
+  minDec.innerText = minutes[0];
+  minUni.innerText = minutes[1];
+  secDec.innerText = seconds[0];
+  secUni.innerText = seconds[1];
+}
+
+// Start/Stop button functionality
+btnLeft.addEventListener('click', () => {
+  if (btnLeft.classList.contains('start')) {
+    chronometer.start(updateDisplay);
+    btnLeft.innerText = 'STOP';
+    btnLeft.className = 'btn stop';
+    btnRight.innerText = 'SPLIT';
+    btnRight.className = 'btn split';
+  } else {
+    chronometer.stop();
+    btnLeft.innerText = 'START';
+    btnLeft.className = 'btn start';
+    btnRight.innerText = 'RESET';
+    btnRight.className = 'btn reset';
+  }
 });
 
-// Reset/Split Button
-btnRightElement.addEventListener('click', () => {
-  // ... your code goes here
+// Reset/Split button functionality
+btnRight.addEventListener('click', () => {
+  if (btnRight.classList.contains('reset')) {
+    chronometer.reset();
+    updateDisplay();
+    splits.innerHTML = ''; // Clear splits
+  } else {
+    const li = document.createElement('li');
+    li.innerText = chronometer.split();
+    splits.appendChild(li);
+  }
 });