"Thank you for playing!" achievement

[LalitoTV]

it is the last achievement, and the only one i dont have, all the others are unlocked as you progress through the game (i.e complete chapters, get crystal hearts)..., except for the 1UP achievement, so i wanna know, what exactly do i have to do to get it? complete all the c-sides? get the golden strawberries? or... get everything on this game...?

[Adze]

Complete the C-Sides

[Ascended]

I dread that I have to now do all of this without cheating just to justify my efforts on becoming a pro at celeste.