flip.js

(function(){
  function handleClick(e) {
    const r = Math.random();
    if (r > 0.1) {
      console.log("not yet: ", r);
      return true;
    }
    e.preventDefault();
    e.stopPropagation();
    s = document.body.style;
    if (s.transform === "rotate(180deg)") {
      s.transform = "";
    } else {
      s.transform = "rotate(180deg)";
      console.log("flip! ", r);
    }
    return false;
  }
  document.querySelectorAll('a').forEach((a) => a.onclick = handleClick);
  document.body.style.transition = 'all .2s ease'
})();

manifest.json

{
  "manifest_version": 2,
  "name": "Flip",
  "description": "(╯°□°）╯︵ ┻━┻",
  "version": "0.1",
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "flip.js"
      ],
      "run_at": "document_end"
    }
  ]
}