Automatic Language Growth is a strict comprehensible-input approach that aims to produce natural language ability by eliminating early speaking and conscious analysis. ALG was developed by linguist J. Marvin Brown originally for learning Thai.
It focuses only on comprehensible input and discourages everything else (no grammar explanations, no dictionary use, a long silence period etc.). So, CI is the only way of acquiring a language.
ALG was most famously implemented in classrooms with two native speakers interacting naturally by using stories, demonstrations, jokes etc. accompanied by heavy use of props and gestures. The learners simply listened and followed what was happened.