diff --git a/content_script.js b/content_script.js
index dfe2f88..dfe5d44 100644
--- a/content_script.js
+++ b/content_script.js
@@ -1 +1,28 @@
-//TODO: Code, der auf trello.com ausgeführt wird
\ No newline at end of file
+function addButton(){
+    const sidebar = document.querySelector(".window-sidebar")
+    const button = document.createElement('span');
+    button.classList.add('button-link');
+    button.addEventListener('click', onClick);
+    sidebar.prepend(button);
+
+    const buttonIcon = document.createElement('span');
+    buttonIcon.classList.add('icon-sm', 'plugin-icon');
+    buttonIcon.innerText = '+';
+    button.append(buttonIcon);
+
+    const buttonText = document.createElement('span');
+    buttonText.innerText = 'Toggl Task';
+    button.append(buttonText);
+    
+    sidebar.querySelector(".js-sidebar-add-heading").classList.remove("mod-no-top-margin")
+}
+
+function onClick(){
+    alert("work in progress ;)")
+}
+
+window.addEventListener("pushstate", function(){
+    if(window.location.pathname.startsWith("/c/")){
+        addButton()
+    }
+})