If a bullet collides with an enemy it kills / removes health (could have a health bar / number above enemies for this). Ensure front of bullet is on different sides depending on the direction it was shot.
If an enemy collides with a player it removes a life from the player
Add collisions with the enemy.
If a bullet collides with an enemy it kills / removes health (could have a health bar / number above enemies for this). Ensure front of bullet is on different sides depending on the direction it was shot.
If an enemy collides with a player it removes a life from the player