it's like DTD... but unlike Xeno Tactics, it acutally IMPROVES upon the base idea of DTD. (Have you ever seen 4 mege mega towers in action!?)
Now, for a bit of advice - Upgrade boosters into mega and then mege mega towers. The boosts will carry over to the tower overall, and unless it's all boosters, there should be a bubble hose, with thousands of damage, the entire map in range, and 1 reload. 3 or 4 of those can carry me well into the hundreds of waves.
nearly ALL of the towers have full map range. the top mega tower is 2 range and 2 slow, the second is 2 regular blast towers and 2 range. the bottom 2 are 2 sniper 2 range. All 4 mega mega are 1 full sniper mega and 3 full dmg boost megas. Seems to work pretty well.