Achievement: Solve 10 4d problems

Solve 10 4d problems

1400 XP

Solve 10 4d problems.

Recently completed by

casjen 1k, superti 1d, Кохэйри 5d, gughi 2d, DariusDobranis 1d, Irina 8k, Vagabonk 1k, pirat 2k, Sang Werner 1d, Bibigul Arzybaeva 1k

and 108 others.