Platypus is a side-scrolling shooter game from Astraware.  Lauren and I reviewed Platypus a few months back.  We both loved the challenging game play, clay-like graphics, and retro music.  You can check out our complete review here.  Astraware has gone and improved an already great game.  The update allows for a multi-player mode over local wi-fi for the iPhone and iPod Touch versions.  Now you can tag team all of those evil ships, balloons, and crazy electric pop cans.