Trying Tinkercad: glacially slow simulation?

Based on several positive articles I'm trying Tinkercad with the familiar Blink sketch. I've seen this in several tutorials apparently working at roughly real time. But here it's glacially slow: at least 20 seconds per cycle.

After much googling I've so far found no explanation. Anyone here used it and have any insights please, before I regrettably abandon it?

Terry, East Grinstead, UK

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