RTS Unit Selection in Unity Tutorial

In this video, I'll show you how to add unit selection functionality to your Unity game. By the end of this video, you'll know how to select individual units as well as how to draw a unit selection rectangle when the player drags the mouse around their desired units.
Link to code:
ISelectable: pastebin.com/k...
Entity: pastebin.com/z...
EntitySelector: pastebin.com/a...