From Eterna Wiki

EternaBrain is an RNA design tool that uses lessons learned from Eterna players' moves to automate RNA design.

More technically, EternaBrain is a multilayer convolutional neural network (CNN) model. The model was first trained on 1.8 million player moves from 12 representative Eterna puzzles. It was then trained on moves from a subset of "expert" Eterna players (players who had solved at least 3000 Eterna players). EternaBrain's performance was tested against that of other algorithms on the Eterna100 set of puzzles.