Thanks for the feedback!

> This kills my back button. What are you storing in the URL?

The URL stores the system rule - the idea being that you can share it. The URL changes over time as you play because playing edits the system rule.

J and K toggle down and up the 'dynamism' in the system. It's semi-random in the sense that you can't control what new system you get when you press J or K, but you will get a system that has either less or more dynamism than the current system. Dynamism is a property of the system - roughly how often 'things change' per the system rule. EG a conditional in the system rule that necessitates an off cell becoming an on cell is a 'thing changing'.

Sometimes I get systems that are too flashy https://strangebinary.com/#111111000100110100001000010010001... Is is possible to eliminate them?

I understand that it's visually unpleasant (not to mention potentially dangerous for epileptics). That said it's literally just a rendering of what the system rule dictates. Lower dynamism systems tend not to be as flashy.

You can map every flashy rule to the equivalent nonflashy rule by inverting all the bits, no interesting behavior is lost.

You can replace history state without appending it

True!