Cool game! Run and gun games like this one are always fun. The idea to add a "fog of war" effect added an extra element of surprise. Now for my detailed review:
Gamplay: 3/5. The run and gun concept is fun but a little simple. The instructions for the controls could be a little better (e.g,. LMB should be spelled out as "Left mouse button," otherwise this will confuse new players.)
Graphics: 2/5. The graphics are simple but cute. The text in the beginning is a little blurry though (may have to do with an anti-aliasing setting). Also, the fog-of-war effect obscures some of the intro text as well.
Audio: 3/5. The sound effects are cute and effective, but I would have liked music.
Polish: 2/5. The game works but there are some obvious bugs, like the fog obscuring the intro text and the victory screen not filling the entire canvas window.
Theme: 4/5. The space setting fits the them well, and the fog of war incorporates the theme into the gameplay. My only gripe here would be that the goal of the game is not to explore the unknown, but to survive it. If I could have put a 4.5 here I would have.
Overall: 3/5.