The problem in this game is that you don't have a evolution. Your character only evolve in dungeon, but when you die you lost everything. There should be some kind of reward to restart games whit some "gifts".
How to get the "Super-upgrade!" real fast: 1 - Start a new game. 2 - On the first launch you must get at least 8 letters, if don't, restart and try again. 3 - Once you get the 8 letters tri to hit the Color Bird and turn the game colorfull, this will make the Troll fly realy fast. 4 - Now do 3 or mor launches and by the "Super-upgrade!", it is worth all the effort and is super funny. Hate this high so other people can see.
I Believe a 5/5 is too much for this game, the only good thing it have is the grafics and the upgrading patern of the towers. It will improve the fun if you put something like a "character" to control the towers and this character level up with the score you get from each level and gain abilities like "get more bones", "send hell soldiers" and ohter things. So its a 3/5. Keep the good work.
Here is my "how to" get long flights: Buy Rudder Control, Lightweight, Crane Booster, Lucky Star and Fire Engine. After this invest in Better Model, Ruder Control, Lightweight, Green Fuel and Aerodynamics. Now the "big deal", the aim is not get high heights but yes stay low and hit as many golden stars, booster cranes and windmills as possible. You will easy achieve 2KM in no time just control your plane and have fun! If you think this is useful rate up so other people can see.
My note for this game: 2/5. Lacks the option of loading the game and them make some changes in the last upgrades. No mute, takes too long to get XP, zombies going to a concrete building barehanded. ... . ..
Maybe if the game have a "character building process" it will be more interesting. For each level up you receive some points to distribute on your tribe and start the next battles whit more resources or more recruits and stuff. Thats what i think. Because sometimes if you can´t win a battle just reenter and with little luck you win.