Difficulty is selected when starting a new game, and cannot be changed later.

In Hard Mode, a few things are different.

-You only get 1 HP every level. HP pickups are still in every level, but don't carry over like normal mode.

-The shop is disabled. You're on your own!

-No dialogue or tutorials. Mostly because if you pick Hard mode, you've probably already played the game and know the mechanics. Saves time.

-Speaking of time, Slow Motion is disabled too. It's pretty OP in normal mode.

-Lastly, you can only charge/shoot an energy shot if your gauge is full

Also, there's a new secret achievement!
...but I'm sure you can guess what it is.