Microsoft Edge. And yes, even if I close and re-open the browser it is still there.
It sounds like there's something weird to do with the way your browser is initialising the seeded random number generator, but I don't know what could be happening or what I could do about it. Playing it in a different browser or clearing your browser's cookies might fix the issue, although you'd also lose your saved game and any high scores. Sorry I can't be of more help.