The plot in Postal Panic is a bit thin: deliver some love letters back and forth here, serve as a communique for a mad scientist there...all that typical jive. Controls aren't groundbreaking either, although in this case, that's a good thing. Use [arrow] keys or [WASD] to move and [space] to shoot. Where the controls do get a bit interesting is when it comes to aiming your cannon, which is controlled by the same keys as movement, although the cannon is locked in place when you're firing. At first, it can take some getting used to, but once you get the hang of it, this mechanic proves useful and unique. Most side-scrollers limit your firing trajectory directly in front of your enemy, and once that enemy passes above or below you, it's out of your reach. In Postal Panic, you can pivot your cannon a full 360 degrees, aiming at enemies above and below you, and even behind.
Game play is pretty straight-forward: advance from stage to stage (delivering letter after letter) with a slew of enemies between you and the finish line. Once killed, enemies drop coins or gems that you can pick up to add to your score. At the end of each level, you can access a "blueprints" menu and use your winnings to upgrade your ship. Spend points on your engine to move faster, buy better armor to increase your resistance to attacks and pick from a buffet of weapons. As you advance through the game, you have a total of eight different "slots" that you unlock each time you buy a new weapon. (Each slot also represents a firing angle from your ship.) You can place different weapons in different slots for a variety of strategies.