Please for the love of god what is the Well done achivement?!

[Raven_pen]

Seriously there is no advice anywhere and I do not understand the absolutely wonderful guide made by Alan. Please can anyone explain in basic English what I need to do? I just want to frigging get 100% on the achievements. I have unlocked all the upgrades to level 14 so I hope I haven't f-ed myself but even if I have I want to know what I need to do.

[Mozai]

I think you gotta buy all the upgrades including 'snake [1/1]", then complete tier 14 (wow it's hard, go into options and choose "easy mode" so the snake only moves on keypresses) and after you get all-nines for your score, one last upgrade appears below "snake [1/1]"