Added some help text to the arena scene
Added a enemy list singleton to track all existing enemies. All enemy behaviours are now derived from BaseEnemyBehaviour which ensures that enemies are properly added and removed from the list as they are created and destroyed.
Also added a script that should've been in the last commit
Added a homing missle ability. Also fixed a bug where Mortars weren't applying their damage
added an option that allows for spawn intervals to be randomised
removed unused script
all projectiles fired by ProjectileAttack derived abilities will no longer collider with the player. This hopefully gets reset also incase the projectile is reused and fired by something else
HomingRockets now fire with the correct facing direction