SudokuSolves/ClockChallengeDemo

The intended start:

Box 5 :

r5c4 = 2
r5c6 = 4
reason : clockwise & anticlockwise dot pattern

r4c5 = 9
r4c6 = 7

reason : clock line + dot pattern

r4c4 = 1
r6c4 = 8
r6c5 = 6
r6c6 = 5

Clock line :

clockwise from r4c7 : 5,7,9,2,4,6,4

reason : clock line plus digits eliminated by those from box 5

arrow starting from r7c7

bulb is a minimum of 4 (length 3 arrow with 121 across border) or 6 (123, if not across border)

Looking at possibilities it must be an 8
Reason: (4,5,6,7,9 ruled out)

arrow starting from r3c7 = 6 (similar reasoning)

other two arrows may also be narrowed down at this stage

use the remaining dots to narrow down options, and eventually they resolve.