// Browser-only clocks; simulation code stays usable without a browser or a clock.
let PERF_MARKS = false, PERF_FRAME = null;
const perfMarks = {}, perfTimes = {}, perfLast = {};
for (const name of ['drawWorld', 'computeLight', 'simMove', 'heatPass']) {
  const original = window[name];
  window[name] = function (...args) {
    if (!SET.showPerf && !PERF_MARKS) return original.apply(this, args);
    const start = performance.now();
    const result = original.apply(this, args);
    const ms = performance.now() - start;
    perfLast[name] = ms;
    if (name !== 'computeLight') perfTimes[name] = (perfTimes[name] || 0) * 0.9 + ms * 0.1;
    return result;
  };
}