Add gym-derk to environments
diff --git a/docs/environments.md b/docs/environments.md
index 7aaeeed66d2..d647435643f 100644
--- a/docs/environments.md
+++ b/docs/environments.md
@@ -304,6 +304,12 @@ A simple environment using [PyBullet](http://github.com/bulletphysics/bullet3) t
 
 Learn more here: https://github.com/JacopoPan/gym-pybullet-drones
 
+### gym-derk: GPU accelerated MOBA environment
+
+This is a 3v3 MOBA environment where you train creatures to figth each other. It runs entirely on the GPU so you can easily have hundreds of instances running in parallel. There are around 15 items for the creatures, 60 "senses", 5 actions, and ~23 tweakable rewards. It's also possible to benchmark an agent against other agents online. It's available for free for training for personal use, and otherwise costs money; see licensing details on the website.
+
+More here: https://gym.derkgame.com
+
 ### gym-abalone: A two-player abstract strategy board game
 
 An implementation of the board game Abalone.

Hi,

I'm the author of [Derk's Gym](https://gym.derkgame.com), which I implemented to be as compatible as possible with OpenAI gym. It's a multi-agent environment though, and as far as I can tell there's no clear consensus on how to handle that. I tried to model the API after the multiagent-particles-env.

Would also love to get feedback on the environment itself!