The first step to learning Chinese is understanding and differentiating all the different syllables. This tool plays a random Chinese syllable and asks you to transcribe it into pinyin. It uses the awesome Tone Perfect dataset by Michigan State University.
This app is completely free and open source. It is very early stage, but still completely functional. Contributions are welcome!
Catherine Ryu, Mandarin Tone Perception & Production Team,
and Michigan State University Libraries Digital Collections Team (2017). Tone Perfect (https://tone.lib.msu.edu/).