12 1. Ne7

If 1 ... Q x N
2. RxQ

if 2 ... RxQ

3. Re8 mate

13

1. Nxc6

if R x e1 capture Q with check

if queen moves Ne7 forking king and rook

if queen captures knight, capture rook with queen


14

1. N x d5 penetrate 7th rank with rook.

15

1. nf7 ch

wins a rook because if bishop takes knight, queen takes knight

after rook takes knight pawn takes knight, rook takes bishop still threatened

16 nf4 intending n xd5

17 bf4

18 nd7 wins piece


Got 5 right. Missed Queen penetration in 14. Missed queen pin after rXn in 16.

I think I'll play some trainingbot.