Black could have turned the corner with

|20.s21 21.s22 22.q20 23.t20 24.r18 25.t17 26.s16 27.u15 28.r14 29.u11

and the battle continues, although I like white's position.

Thanks for posting that. Looking at the endgame position, I was wondering if I was losing my touch, thinking "why not |20.s21?!"

I'm not sure I like white's position so much. After
|20.s21 21.s22 22.q20 23.t20 24.r18 25.t17 26.s16 27.u15, 28.r14 is a natural local reaction, but the top of the board is still pretty wide open. Instead of cutting off your path up the middle, and leaving your run up the right side open, he could have made use of his across-the-top threat, with something like 28.o7. What then?

|20.s21 21.s22 22.q20 23.t20 24.r18 25.t17 26.s16 27.u15 28.o7 29.s7 and then:

30.r14 31.u11 or
30.r10 31.s14 32.k7 33.r9 or
30.q8 31.s14 32.k7 33.r9 or
30.r9 31.t9 or
30.s11 31.s14 32.k7 33.q8 34.p9 35.p10 36.o11 37.t12