The game prototype has been updated (0.4.1):

• Difficulty settings added: Beginner (a bit easier than older versions), Normal (the exact same difficulty as before), and Survival (a bit more challenging experience).
• Gameplay Balance Data: the game now collects anonymous gameplay balance data (if you defeated 0, 1 or 2 bosses, detect where the player has problems etc.) to help balance the game in the long run. You can turn this off on the menu screen if you don't like to participate in the balance data collection.
• Some bugfixes.

For the future a sandbox/custom difficulty setting is planned to tweak the difficulty settings to your individual taste.

Have fun,

Matt