Heavy Gunner 3D is a satisfying if repetitive sci-fi-themed arcade shooter with short, fast-paced levels and an RPG-style system for buying and upgrading weaponry.
Heavy Gunner 3D's most striking feature is its 3D-ness: from your fixed first-person perspective, you look down the barrels of your two guns (one on the left, one on the right, controlled with touch-screen thumb-joysticks), but you can tilt left or right to rotate your view 360 degrees, and you can tilt forward and back to look up and down. This makes for physically involving gameplay, as you rack up kills and chains on large squads of squidlike alien fliers, with an independent targeting reticule for each weapon. The controls can occasionally get unresponsive amid all the action (and older devices will have trouble keeping up unless you downgrade your settings), but for the most part the twin-gun interface is fun and quick. You'll want to quickly buy a second weapon (you can choose from optical, missile, machine-gun types), since you can switch weapons during reloading. The game's point system lets you buy additional weapons and upgrades after each level.
The controls of Heavy Gunner 3D have been improved in recent updates, and the game's only notable weakness is its repetitiveness over 35 levels (with three difficulty levels and a Challenge mode). Fortunately, if you like shooting things, you might not notice much.