diff --git a/app.js b/app.js
index 858ff28..2b9b074 100644
--- a/app.js
+++ b/app.js
@@ -24,10 +24,14 @@ const displayTime = () => {
 
 document.querySelector('.btn-primary').addEventListener('click', (event) => {
     startTime=Date.now();
+    document.querySelector('.btn-primary').disabled=true;
+    document.querySelector('.btn-secondary').disabled=false;
     windowInterval = window.setInterval(displayTime,1000)
 })
 
 document.querySelector('.btn-secondary').addEventListener('click', (event) => {
+    document.querySelector('.btn-primary').disabled=false;
+    document.querySelector('.btn-secondary').disabled=true;
     window.clearInterval(windowInterval)
 })
 
diff --git a/index.html b/index.html
index 3c943bc..44d4da1 100644
--- a/index.html
+++ b/index.html
@@ -12,7 +12,7 @@
     <body>
         <main class="container-fluid">
             <button type="button" class="btn btn-primary">Start</button>
-            <button type="button" class="btn btn-secondary">Stop</button>
+            <button type="button" disabled class="btn btn-secondary">Stop</button>
             <h1></h1>
         </main>
         <script src="app.js" charset="utf-8"></script>
