Funny I found a way to slow a bit the game by only playing with 2k stars :)
As a developer I know how tricky the tick & rendering stuff is.
Maybe some dt var (elapsed time since previous tick) could help to avoid having a game running fast just because the hardware can
If i'm not clear, you can see it (it's a codepen of my own) here in the JS part : function __Tick
anyway, great game ! Keep it up