Reverse Clock Bookmarklet - This handy tool counts down the time you set, helping you stay focused and improve your estimation skills for tasks like reading articles, watching videos, or completing online assignments.

ReverseClockBookmarklet.js

javascript:(function() {
  var t, ts, h, m, s, u, c, tmr, f = document.createElement("div");
  f.id = "revClock";
  f.style.cssText = "position: fixed; top: 10px; right: 10px; background-color: rgba(0, 0, 0, 0.5); padding: 10px; z-index: 9999; text-align: center; font-size: 20px; color: white;";
  document.body.appendChild(f);

  t = prompt("Enter number of minutes:");
  if (t === null || isNaN(t) || t < 0) {
    alert("Invalid input. Please enter a positive number for minutes.");
    return;
  }

  ts = parseInt(t) * 60;
  u = function() {
  h = Math.floor(ts / 3600);
  m = Math.floor((ts % 3600) / 60);
  s = ts % 60;

  tmr = h.toString().padStart(2, '0') + ":" +
        m.toString().padStart(2, '0') + ":" +
        s.toString().padStart(2, '0');
    
  if (ts <= 0) {
    clearInterval(c);
    tmr = t + " minute(s) up!";
  }

  const n = new Date();
  var fn = n.toLocaleString("en-GB");
  f.innerHTML = tmr + "<br>" + fn;

  ts--;
  };

  c = setInterval(u, 1000);
  u();
})();