Great potential
The game is very good. However there are some suggestions that should be looked at. I also found a bug.
SUGGESTIONS:
1) A save feature is definately needed for the achievements. There is a Reset player data on the main menu, but I didn't see any save button. Though I may have missed it as I did the help button (indicated in suggestion 3). If you have to be on the sponsor's home page to save, you should say so in the comments or in the menu or instructions.
2) Scores need to reset after beating them. You can easily just keep playing a level and increasing your score to make top scorer.
3) Better instructions: Show what the power-ups work by showing how to use them. And with Non-power-ups like health and poison, put a short note at what they do. I know that it seems obvious, but like with poison, in RPG's they gradually lower health, while in this game it just lowers health to a certain point but doesn't kill the player. Also, the medikit only heals X amount.
3a) Better placement for instructions: I unlocked a weapon, but didn't know how to get it into play. I didn't know how until went back to the menu screen and found the question mark at the bottom left. I guess I didn't see it because when the menu came up, my eyes went to the pillar that the guy was looking at. Which seemed to me the only options.
4) A pause button. It is good to have one when the player needs to pause the game for any purpose.
5) Tell the player that they have extra weapons on certain levels. I had to find this out the hard way. I thought it was a bug. Maybe have a weapons button that goes to a page that shows the weapons that the player has aquared. Possibly show stats to each weapon, maybe some upgrades.
6) There seems to be little point for a reset button as the guns seem to reset on their own rather fast. Maybe change the guns reload speed, so that the reload button will have a purpose. This could be on the weapons page mentioned on suggestion 5.
7) Possibly have armor ratings and have the health bar show health in numbers. The different armors can have different ratings numbers shown on a page. Maybe with the weapons. This page could have tabs or buttons of it's own for the stats of each weapon, and onther for the stats for each armor. And so forth.