Good stuff.

Graphics:
The graphics are great, with good resolution when maximised. Each sprite is simple yet effective.
Sound:
May have been my computer, but the game had no sound whatsoever. If it was my computer I'll re-rate it.
Gameplay:
Very simple; just warm up your weapon and start killing everything. It gets very repetitive after a while, but is fun to play for a good ten to fifteen minutes. It can take awhile to earn enough funds for the better weapons and levels. The initial weapon takes too long to warm up (over five seconds), and could be faster.
Story:
N/A
Interface:
The WASD controls are familiar, but the rotation/movement takes a LOT of adjusting to. At some points more attention needed to be paid to just moving rather than killing. The shooting direction controls (mouse) worked perfectly.
Overall:
A blast to play for awhile, but can drag. A great job from the maker.