Asp Boss

This is a particularly difficult level if you just start to place all your towers at once and don't have enough airborne firepower.

The strategy you should employ is to place two mortar canons, one on the power up anomoly and the other on the other side of the map - along with a cheaper tower (eg a detector).

Place a couple of strong air defenders near the path that the enemy would take to go up past the prime reactor on the right - but don't block the path.

When the boss approaches the prime reactor, block his path, he will then try a different approach - block him again, and continue to do so until he takes the final path back behind the reactor where your strong air defenders are - see the screenshot for a general idea of what I'm try to say. Easy three stars and hopefully some great cards if you kept a clean sheet!