TL;DRSuggest to make the end of the game much more interesting, challenging and frenetic.
What ?What do I suggest is that the player needed to create and enormous machine composed by modules that you will need to place on the terrain in order to complete the entire machine. This machine, will provide the antimatter fuel needed for the spaceship to work. But this machine has an inconvenience... Once it is turned on, it will take a long time to produce the fuel and while it is working, it will atract all the bitters of the planet and at some point, the bitter's queen itself (a worthy adversary for the robotic spider). Player will need to plan the defense and gather resources to keep the defense up during the siege.
Why ?Something I expected when I was finishing the game was a climax like this, but never happened. I think this suggest will make the end more interesting, and also will force the player to focus more on the defense of the factory (something that right now, adding some walls and a few lasser turrets it is solved)
Note: It this suggest interest you, I have a few others to improve this one.