In the third line of the "strategy" function: def strategy(observation): score, dealer_score, usable_ace = observation **# Stick (action 0) if the score is > 20, hit (action 1) otherwise** return 0 if score >= 20 else 1 **"> 20" should be ">= 20"** Also, the same typo in the "sample_policy" function, in the "MC Prediction.ipynb" file. Thank you for your hard work!