base
Each candidate hashes the word before it with a 64-bit little-endian counter appended: sha256( word ‖ counter ). But I can't be a girl! seeds the chain.
ascii8
One byte per character. A match means the SHA-256 hash prefix spells the word in ASCII hex.
targets
yes, you, can — the answer ground word by word from the exclamation, each successively longer prefix match kept.
counters
Winning counter values from 3.8 million to 43 million, within a 248 budget per search.