So with two achievements to go (not including a couple of Shadow achievements) I just noticed 'Hardcore', described as:
'Get to 1 billion cookies with no upgrades purchased.'
I haven't got this one yet so it sems that I might ascend again in the morning and go for that one. I'll obviously need to activate Challenge mode for that.
Any thoughts on how long it'll take to reach a billion without any upgrades whatsoever? It's been a long time since I started clean.