This article is written by Chintan Trivedi. Proximal Policy Optimization aka PPO was released by OpenAI in 2017. It is considered as the state-of-the-art algorithm in reinforcement learning. The USP of this article is its simplistic explanations and coding of PPO as well as the accompanying videos. The author also released the code in his github page.

https://towardsdatascience.com/proximal-policy-optimization-tutorial-part-1-actor-critic-method-d53f9afffbf6