We need to handle collisions between our enemies and ActiveBarriers. Since we have a Rigidbody attached to our Enemy prefab, it will receive the
OnTriggerEnter() event when it hits the collider of an ActiveBarrier GameObject.
Once the collisions with ActiveBarriers are implemented, we'll add collisions with the bottom of the screen, which will reduce the player's health.
First of all, we must disable the ActiveBarrier's collider by default and enable it when the barrier is built in the following manner:
ActiveBarrierController.csscript attached to it.