A useful tip: In some levels, you can deploy your orbital next to some creeper devices at the beginning of the game and build a nullifier right away. Your orbital might take some damage, but once the job is done you can relocate it. Useful to take out the anti aircraft creeper device on the last level for example.
How does one unlock the other 2 titans, berta and thor? You can use two bertha in the 14th level, but you cant make them somehow. They must exist because in the settings they have a key-bound
 "Creeper World 3: Abraxis"){kind=icon}
 "Kick The Critter"){kind=icon}
 "Dream Car Racing"){kind=icon}
 "Bloons Super Monkey 2"){kind=icon}
 "Cursed Treasure 2"){kind=icon}
 "Don't Shit Your Pants"){kind=icon}
 "Reactance 2"){kind=icon}
 "Terra Monsters"){kind=icon}