The Umbra decoding challenges were excellent
Lots of interest. Lots of head scratching. Lots of fun. The miniciphers had a good variety of easy to difficult, and the master codes were mind bending, to say the least. In terms of trying new things with anomalies and keeping them fresh, I think the decoding challenges were a winner.
There was just one fly in the ointment: Getting locked out of entering passcodes via the intel map. Not everyone has an Android device handy.
I appreciate that Niantic doesn't want anyone brute forcing passcodes. However, during the anomaly, with all of the miniciphers and master codes, I do think it is reasonable to expect that one agent will solve quite a few miniciphers and make quite a few attempts at the master codes. A cool down on intel lasting for an hour feels unnecessarily punitive.