From what I understand, endless mode is currently trivially easy due to refined fundamentals being bugged and/or overpowered, as well as other possible issues like integer overflow.
But some of you seem to be enjoying it nonetheless, so I figured I'd go ahead and unblock your progress. Do keep in mind that as I'll be making endless mode slower/more difficult in the near future, you may prefer to wait until then to play it so you don't feel as though you're cheesing the achievements.