Hi numeromancer, I am surprised to hear mention of Engelmann and Project Follow Through here on HN :). I would love to connect and learn more about how you discovered DI. FWIW, I am a former principal engineer at a FAANG company turned educational researcher / edtech founder. I am working to revive Engelmann's Theory of Instruction and democratize access to the explicit, systematic teaching of the skills of reading (e.g., phonological awareness, decoding, and sight recognition).