I tworks

background.js

@@ -6,7 +6,7 @@ chrome.runtime.onInstalled.addListener(function () {
   chrome.declarativeContent.onPageChanged.removeRules(undefined, function () {
     chrome.declarativeContent.onPageChanged.addRules([{
       conditions: [new chrome.declarativeContent.PageStateMatcher({
-        pageUrl: {hostEquals: 'youtube.com'},
+        pageUrl: {hostEquals: 'www.youtube.com'},
       })
       ],
       actions: [new chrome.declarativeContent.ShowPageAction()]

contentScript.js

@@ -1,9 +1,14 @@
 function applyDefaultStyle(element) {
   element.style.position = "fixed";
-  element.style.zIndex = 1000;
+  element.style.zIndex = 99999999;
+  element.style.color = "#FFF";
+  element.style.backgroundColor = "rgba(0, 0, 0, 0.5)";
+  element.style.padding = "0.25em 0.5ch";
+  element.style.fontSize = "3vmax";
 }
 
 let mCalorieCount = document.createElement("div");
+mCalorieCount.id = "ykonsole-calorie-count";
 applyDefaultStyle(mCalorieCount);
 mCalorieCount.style.left = 0;
 mCalorieCount.style.top = 0;
@@ -15,6 +20,7 @@ mCalorieCount.innerHTML = `
 document.body.append(mCalorieCount);
 
 let mResults = document.createElement("div");
+mResults.id = "ykonsole-result";
 applyDefaultStyle(mResults);
 mResults.style.right = 0;
 mResults.style.bottom = 0;

manifest.json

@@ -18,6 +18,7 @@
     "storage",
     "activeTab",
     "declarativeContent",
+    "https://www.youtube.com/",
     "https://indigo.stian-aune.com/"
   ]
 }