Brings me back to sweet memory lane of the arcade style Contra series of Nintendo with a twist.
People relate it to Doom 3 for the plot premise or Diablo II for its gameplay style but none of them are a fair comparison to this humble game. I feel that Shadowgrounds did not try to capitalise on the current trend of popular hits like the above mentioned games but it's more of aiming to bring back the old-school way how games should be played. A top-down shooter is very retro, like the earlier Sega games Contra and Master of Elements and these are the games that started the world of video-gaming. Shadowgrounds was going for this, from the gameplay mechanics to the simple story premise.
Other than that, it does feature contemporary elements like upgrading of weapons to give it a role-playing feel and that each weapon has it's own advantage in certain situations without giving you the lame idea of sticking with ultimate weapons ultimately.
One thing makes it different from retro shooters and that is the graphics. Very nice backdrop and great particle effects (like explosions and the flamethrower) refurbish the looks well enough to attract new generation of gamers. Great music tracks. An overall enjoyable game for a week.
KingLim