For a great collection of info, see Skidushe's excellent thread.
Also check out these instructional videos to get started; One covering the basics, and one covering Monitor Distance in details:
Version 7.5.a (November 18, 2018) - This is a brand new version with support for multi-calculations, see this thread for info!
The old version is available here so you can check if you encounter a bug.
New games: Creative Destruction, KovaaK's FPS Aim Trainer, Sword Art Online: Fatal Bullet, The Long Dark, Fallout 76, Project Warlock.