The practice of focusing on specific words in these texts called huatou was introduced by Dahui Zonggao. The concept of mu is often illustrated in these texts, as in one that asks whether a dog has a certain nature. Wumen Huikai made famous commentaries on these texts, which are compiled in (*) The 
The practice of focusing on specific words in these texts called huatou was introduced by Dahui Zonggao. The concept of mu is often illustrated in these texts, as in one that asks whether a dog has a certain nature. Wumen Huikai made famous commentaries on these texts, which are compiled in (*) The Gateless Gate and The Blue Cliff Record. Hands clapping without making sound are discussed in one of these texts, which are used to test students in the Soto, Obaku, and Rinzai schools. For 10 points, name these stories used to teach Zen Buddhism.
The practice of focusing on specific words in these texts called huatou was introduced by Dahui Zonggao.
(Zen) koans [or gōng'àn; or kongan; accept collections/compilations/books of koans; prompt on "Buddhist stories" or general answers that do not give the specific term from Zen Buddhism]