Solution: The primary issue was choosing the wrong setting for "pin orientation" with respect to the values I used in my code. There are lots of good details for beginners in the responses below regarding pins, bits, and naming... I've been working with the ATTiny85 then ATTiny84 and next I want to…

[Solved] Switched from "attiny" to "ATTinyCore" package, can't blink an LED now

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