Well down my comments for no reason... @Ping trading is trading ITEMS. Auctioning is where people bid on items till the price gets higher and higher. Buying is the system we have now.
I jumped up to the laser and fell down before it activated, in the hopes it would rise up and i wouldn't have anything chasing me. Well what happened after that was I was stuck and in the background a troll face appeared. You should check it out xD.
First I won't rate this game because giving it a 5 would be a disgrace. It's an awesome game. However I do have some suggestions. The first one is an upgrade to the barracks to add one more troop when built. The second suggestions is to be able to modify where towers attack. I can't tell you how many times I have lost a life just cause my tower would attack the wrong type and not what I wanted it to. My last suggestion is being able to station troops wherever you want not just in the rally point area.
The best thing is get a hunter. Invest in a rifle. Buy the best bows and recruit three people who have big guns. With three gravity guns on your side you can take on the ranged with your bow gun. I can deal 300 damage by level 10 with the bow.