I'm on Cosmolite, and I think I have a general strategy for this game.
You first mine the rock that can give you the most money/second for a little while. Then you spend it on upgrading the blacksmith on various stats. Then you mine the rock that you can one-hit kill to farm gems. You do that for a while, and you use the gems to upgrade your pickaxe.
Then you move on to the next gem that gives you the highest money per second, and rinse and repeat until infinite.
It's pretty much Gem TD. The secret is to build a maze that encloses corners 1,3,5 or 2,4,6, so they mobs have to travel in and out of your maze to get to each corner.
It's not the games fault its laggy. Flash just cant handle intense games like this.
I mean rendering what... 700 ballons on the track + another like 200 projectiles is hard work.