Star Defender

You are defending a transport making it's delivery while enemies try to destroy it. You need to build, maintain and upgrade turrets through out your play through. 

The turrets are automated you just need to get close enough and they will fire. You will need to refill the turrets using your ships power supply. You may upgrade individual turrets as well as the ship's propulsion systems and power capacity and recharge rate. 

The B button in the bottom middle will temporarily boost your ships speed at the cost of the ships power. While upgrades cost resources you collect for destroying enemy ships.