Spread the ranged towers out, and they will keep constant firepower on any units that break through your chokepoints. Clustering all your ranged towers together is a bad idea as once those fast-moving units slip out of tower range, they are no longer taking damage.
Vehicle-based enemies, like speeder bike riders, can zoom right on by the melee units. The enemies in Galactic Defense often come into the game as one long stream of units. They Travel Single File To Hide Their Numbers So, say a wave of six enemy units is approaching, the melee tower will keep half of them busy while the ranged tower picks off one or two of them, and then you only have to deal with the one or two stragglers that made it through, at your next choke point. This will break the wave of enemies up, as at least three enemy units become tangled up by the melee units.
I’ve found that the best way to survive for long in Galactic Defense is to make multiple chokepoints by paring up a melee tower with a ranged blaster tower.
