Difficulty level adjustment :-
Lowest difficulty, ship armour regenerates, also gives a few easy levels at the beginning of the game so you can get used to the game mechanics. Recommended for first playthrough.
Enemies shoot more and are harder to kill, your armour does not regenerate you will have to use power cores to bolster it.
Some enemies have homing plasma bolts that try to curve toward you, bullet hell.
If you started playing already and it is your first run through the game you may want to drop down to the new normal difficulty.