A couple of hints: It's almost identically and vertically symmetrical with the exception of the top left corner, which has an addition r5,c2 and r2,c5 - the 4 3 and 3 3 rows/columns(5,19) make an arrow point inward) - Everything with the exception of the centre piece is connected
If you're still stuck, the centre piece (which is not connected to anything is: r10:c10,12,14 r11:c11-13 r12:c10-14 r13:c11-13 r14:c10,12,14.
It's almost identically and vertically symmetrical with the exception of the top left corner, which has an addition r5,c2 and r2,c5
- the 4 3 and 3 3 rows/columns(5,19) make an arrow point inward)
- Everything with the exception of the centre piece is connected
If you're still stuck, the centre piece (which is not connected to anything is:
r10:c10,12,14
r11:c11-13
r12:c10-14
r13:c11-13
r14:c10,12,14.