Chess platforms invest heavily in anti-cheat systems (like Chess.com’s "Fair Play" algorithms or Lichess’s "Irwin"). They fight userscripts in several ways:
(function() 'use strict';
// === END CONFIG ===
function highlightLastMove(board) // best-effort: find last-move squares or elements and mark them // Example selectors (override per-site in CONFIG if needed) const lastFrom = document.querySelector('.last-move-from, .move-from'); const lastTo = document.querySelector('.last-move-to, .move-to'); [lastFrom, lastTo].forEach(el => if (el && el.classList) el.classList.add('tm-last-move'); ); tampermonkey chess script