At first I thought that this is not good. But then I realized: I judged it as a big game. That is how much I was immersed into it.
This small game delivers fast-paced, dynamic shootout Crimsonland-style(not Contra) with easy, intuitive game controls and gameplay. Addicting as hell, too!
Every detail is working as it should, and nothing stands in the way of non-stop bullet hell fun.
This game also provides nice difficulty curve, with later levels becoming erratic with gun-fire and enemies coming from every direction, but this only adds to overall level of fun, thanks to frustration-preventing mechanic of respawn. That way even if you die in a tight spot you can continue your carnage few seconds after, provided your supply cache isn't destroyed.
Sound is pretty default, but good, as well as music that gives good tempo for gameplay.
Graphic sprites ripped out from Counter-Strike: Source looks good as well.
A few let-downs though: I honestly don't see any reason to level up anything other than your default AR, until you level cap it. Other stats are completely unrequired to keep up with enemies until you get bored after few hours.
Level up sound makes a dissonance with other sounds.
To sum it all up: a great time-killer.