Once you get a lot of income, you can just buy dozens of population and growth buildings, making it much easier to get population. I ended with getting about 100 people per day just by placing town halls and churches.
What I don't like about the game is the inconsistency. Some surfaces that aren't ice act like ice. When jumping off a icy platform, sometimes the air controls feel like ice. There is a level in World 6 that is clearly spiked, yet doesn't kill you. The levels in world 3 have spikes so small that you would think they are a platform unless you step on them. Jumping on an edge of a platform may make you stay on the platform, but might also just slide you right off. Ghosts in World 6 sometimes don't stop when you look in their general direction. Dragons in World 10 make each attempt random due to their movement. World 7 trophy says to not use the powerup, but what you actually need to do is collect the powerup and not use it, instead of not collecting it at all.
Tip: In the beginning, try to get everything if you can. If a powerup is blocked skip it. Invincibility is very powerful. Once you get to the EMP minefield, stop focusing on powerups and instead focus on survival. Only go for powerups if they are directly in front of you. This will make sure that you don't mess up your run because of a powerup on the other side of the map.
After you beat the game, instead of pressing enter, just keep going to the center of the map. After some time, you will go back to the start, but with your gun, score, and coins intact, basically making it a NewGame+. Now you can collect the rest of the coins and kill the rest of the enemies for the best possible score.
The hardest level is probably Level 3. Kept getting stuck on it multiple times, but when I finally beat it, I managed to beat the other levels first try.
The best fast attack is the triple shot at close range. The archer has this attack and is unlocked in the beginning of the game. The best slow attack is the three hands technique which can kill a dragon in two uses. The next best slow attack in the triple fireball, but only when used in close range.
For later levels, build your houses at the highest possible point. That way, you can use water storms repeatedly without even wasting any soldiers on fighting them. It also covers the whole map, so all other enemy tribes will get caught in the blast.
For the last level, the level runs slightly faster if you don't shoot and just bounce on all the walls. You don't need kills, and since enemies can't aim at you, you will pretty much take no damage.
Dual machine guns combined with damage buffers are extremely powerful. If that doesn't work on armored enemies, multiple rocket launchers with reload upgraded does the job as well.
 "Boom Town"){kind=icon}
 "Aspiring artist"){kind=icon}
 "The Darkside Detective Demo"){kind=icon}
 "Pandemic 2"){kind=icon}
 "Vertigo: Gravity Llama"){kind=icon}
 "Vector Runner"){kind=icon}
 "Fracuum"){kind=icon}
 "Bloons Tower Defense 2"){kind=icon}
 "Doeo"){kind=icon}
 "Frantic"){kind=icon}
 "Great Dungeon in the Sky"){kind=icon}
 "Papa's Wingeria"){kind=icon}
 "Tales of Nebezem: Droid's Quest"){kind=icon}
 "Feudalism"){kind=icon}
 "Reprisal"){kind=icon}
 "Hover Bot Arena"){kind=icon}
 "Sugar, sugar 3"){kind=icon}
 "StormWinds 1.5"){kind=icon}
 "Dark Cut"){kind=icon}