Interesting puzzle! A minor nitpick: at ~1:45 you narrow the top to two options, but without using the global reasoning discussed later in the video, I don't think you yet had a way to eliminate a 3rd option, which is two separate narrower arches in columns 4/5 and columns 7/8?
Fair point -- My later comment about only having 3 more horizontal segments in rows 3/4 would be what I would have stepped back to to confirm that C4/5 and C7/8 could not be used together to work here. (It would also have "failed fast" but I would have learned the constraint better.)
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Interesting puzzle! A minor nitpick: at ~1:45 you narrow the top to two options, but without using the global reasoning discussed later in the video, I don't think you yet had a way to eliminate a 3rd option, which is two separate narrower arches in columns 4/5 and columns 7/8?
Fair point -- My later comment about only having 3 more horizontal segments in rows 3/4 would be what I would have stepped back to to confirm that C4/5 and C7/8 could not be used together to work here. (It would also have "failed fast" but I would have learned the constraint better.)
You always impress me with how quickly you think.