Right, i’ve finally cracked it. The key as people have said is to use longer range towers and orbital weapons. The biggest thing I had to do different from normal was to use a Canon thingy. Those orangy red critters were the biggest problem, until my defenses were good I used an orbital weapon with them each time.
I’ve attached three images showing progress, I only started taking them once I knew it was going well. From memory I started with a laser tower thingy, then added a Canon tower, and added the slow towers early on.
