Above blamable...
But well below applause worthy in the way of games.
Something is missing that turns the "objective" into an actual story. There is nothing here besides your word that the evil empire is evil. By the end I was hankering for some story based enemy. A warehouse of goods stolen from the homes of exiles and we need to collect the property. A bunker of missiles to be launched at civilian rebel camps. Maybe, and this is a shocker, some sort of boss.
Your method for inferring a third dimension is interesting but it is nothing more than a tiered two dimensional game with the ability for the units to shoot between tiers. This has proven to be somewhat clumsy and annoying in previous games and is not much improved here.
The game was overall rather anti-climactic, and seemed to be a victory by attrition rather than any real resolution.
Pros:
-Love the way you get enemies into the fight.
-The music was OK for the first level.
-Decent graphics and awesome artwork.
Cons:
-No real conclusion.
-Each level needed its own music and something less repetitive therein.
-Neither 3-d nor 2-d = bastard child game play.
-Graphics fail to compensating for poor game design.
-Ammo and health is something you should allow the player to pick up by walking over them.