Slightly altered version of "Bobblehead Wars" from raywenderlich.com tutorial book "Unity Games by Tutorial" 3rd Ed. (two thumbs way up)
##Changes from original tutorial
-- Added UI for health and enemies remaining
-- Added gameover panel to reset the game or exit (Only from build)
-- Allowed gun upgrade to spawn multiple times
-- Added free camera controls, controlled by mouse movement
-- Changed player movement from World space to local (Player) space
-- Animated all arena walls seperately
--Added navmesh obstacles to arena walls
- Aliens now do not walk through walls (most of the time, they're tricky little buggers)
-- Altered wall collision to be between camera and wall instead of player and wall
- This was a result of allowing for camera rotation
-- Added a general Object Pooler
- Items that are pooled: only projectiles currently