Not only is this one of the most fun 2D games ever made, it's simply one of the most fun games I have ever played.
The weapons are all great, the level layouts are near perfect, and the graphics are done just right for this style of game (in terms of dimension and atmosphere). The devs of this game really showed a lot of love for what a 2D game can really be in the modern gaming culture.
This is one of the few action games I feel like I will be able to go back and play several times over without getting bored of the game.
The game isn't very long, but it certainly provides a nice challenge and harder settings and offers plenty of fun exploring options throughout the game. The flashlight used as a special weapon indicator was a really great idea, even if primarily borrowed from the metroid games.
Anyone, especially metriod fans, should buy this game right away as they will no doubt fall in love with it as much as I did.
I really hope many more arcade games like this end up on the marketplace as this was one of the best gaming distractions from the "too many FPS" syndrome we all feel.