Very nice game. Although it is a bit simple. Just make sure you got the maximum number of elevators and load them with machineguns. When you got enough money left replace one gun by a laser and you got no problems.
I've got a strategy which makes the Kongregate Badge really easy. Buy 2 apocalypse cannons and upgrade reload with both. With the remaining money you can just buy a heavy cannon whose damagu u upgrade to max.
The first few enemys can be destroyed by the cannon. When the screen gets filled with more or bigger enemy use one apocalypse. Kill small enemy with heavy cannon then use other apocalypse when things get messy again. Next time you get under heavy attack the first apocalypse should be ready again. This worked the first time I tried even though I triggert one apocalypse accidentially in the beginning.
The game would be much better if you could control bots instead of just giving diffident suggestions.
About that challenge 4. You got best chances if you let shield follow dragon and control sword. But be wary dragon has minimal range so it won't attack shield while they're next to eachother. Wait for dragon moving towards sword. If you're lucky shield will follow with a delay so dragon will attack shield. This is the time for sword to attack dragon from afar. Make sure to get out of range when dragon approaches the wall, because then shield will close the distance again. Then repeat. This might take a few tries though. I hope this helps a bit.
There is no frying pan in this game 0/5 gngngn.... ;-p
Now seriously. The game is really entertaining. Although i don't like that you have to spent money to unlock some items. Apart from that flaw you can say the game has everything to make you spent long time playing it. 4/5.