To gain invulnerability, simply go to the game directory, open the run folder, and open the Difficulty.txt file, change everything under damage0 to 0.0, originally these were, I think, 0.17 0.23 0.3, after you change this you will take no damage in the game other than falling or collision damage. If you change the settings under Damage1 from 1 to 2 you will deal double damage with any weapon, 3 will give 3 times and so on a so forth.