from the start of the game there were problems. First, you don't start the actual game, then suddenly pause the game in mid-combat to show a tutorial balloon, then resume, then do it again, then resume, then do it again. You get the picture. Second, the units at the beginning could be slower, maybe have 2 levels of troop types before you throw in rocket launching jeeps by level 2! Or mechs at level 3. Even with 3 turrets, mechs distracted you too long to defend against the zerg rush of troops and jeeps.
Horrible game. The maker must also think players are 8 years old. You have a turret, it shoots the baddies running towards your wall. Kill them or you die. Pretty straight forward. Try it. And try making a tutorial separate from the actual game next time.