The Chinese for English course teaches Mandarin Chinese to speakers of English.
As of 21 September 2017, no official announcement by Duolingo has been made regarding this course. However, these images from user Seohori depict a conversation with a staff member regarding the approach of such an announcement in late September of 2017. It also mentions that the tree design would be done by the staff with volunteer input.
As of 12 April 2019 the course has 3,240,000 learners.