I have to say, I've bought almost every upgrade, but the one that made the most difference was the (possibly copyright-infringing) Iron Man suit... it's just so helpful.
In later levels, I find myself simply scanning the map while scoped rather than picking them out in the wide view. When the targets are so small and often stationary (or even popping in and out like those five underwater), it feels like a waste of time to even play a level with no variety or change in outcome. Maybe if there were reactions to the gunshots, either by the environment or the targets, or if the player only had a certain number of bullets... until this game becomes more three-dimensional, 3/5.
One should be able to discard more than one card per round... I've found my deck clogged with useless knights and archers when my enemy is at 91 castle and 64 fence, and I am at a similar spot. Once the player has plenty of supplies, one might as well use the cards if there's nothing to gain by discarding them.
Heh heh... oil and water don't mix.
This is a maddeningly addictive game. If you're stuck, stop thinking logically about the combinations (How the heck did I get fossil fuels before dinosaurs?) and add things that don't make any sense. That's the best plan.
Controls seem really sluggish and... heavy? Not sure what the right word is here, but they seem slow on response. Also, I don't really see where you're going with this... it's kinda like one of those pixel-thinking-artsy games (which I usually love), but you're missing a couple cutscenes...
A little boring after a couple levels. Also, the music gets really annoying after the first level. Coconuts are pretty easy most of the time; not sure why they give you achievements. I think it should show you where the banana is in each level before you begin. 3/5.
You get points for knowing the word "ossuary," but it gets a bit old after a couple levels. Try putting it in a more interesting setting rather than white skulls on a black background.
Not very fun, just a boring hangman game like TheNuke said. And jimmij, there are only 50 states. ;) At least you don't live in the US, or else I would be afraid for our world.