TherapieGo: B1, B3, A4 is wrong for no reason. Also, A2, C2, D1, A4, A3 is wrong because when you play C1 to trigger the ko, the opponent can ignore and you still have to add A1 to start the 10,000-year ko.The real sequence should be A2, C2, D1, C1, A4, A1, A3 and 10,000-year ko. Don't forget to add it on the symmetry ;)
Thank you, Lyde, for adding.