Create tooltip.js

It's a mod that adds a tooltip that shows the description of a hovered element at the bottom of the screen.

mods/tooltip.js

@@ -0,0 +1,21 @@
+const defaultTooltip = "---";
+let tooltipEle;
+window.addEventListener("load", ()=>{
+  tooltipEle = document.createElement("p");
+  tooltipEle.innerHTML = defaultTooltip;
+  document.getElementById("extraInfo").children[1].appendChild(tooltipEle);
+  let buttons = document.getElementsByClassName("elementButton");
+  [...buttons].forEach(button=>{
+    let ele = button.getAttribute("element");
+    button.addEventListener("mouseenter", e=>{
+      if(elements.hasOwnProperty(ele)) {
+        if(elements[ele].hasOwnProperty("desc")) {
+          tooltipEle.innerHTML = elements[ele].desc;
+        }
+      }
+    });
+    button.addEventListener("mouseleave", e=>{
+      tooltipEle.innerHTML = defaultTooltip;
+    });
+  });
+});