Wonderful game!
having a variety of mission types and difficulties is a great idea! The simple interface is helpful as you an focus on the mision and not have to remember any advanced controls.
It needs to be said however, that the THEL weapon needs the ability to target a specific enemy or enemies (name or threat level) because when a large group of smaller enemies is attacking your base and you are faced with 3 or more motherships, you tend to be defeted because they are not fired on.
Nice music and good simple graphics. Shop.upgrade system is well designed.
Keep up the great work!