Rather hard and the restart button should restart the mission with your ORIGINAL state in the beginning of the mission.
This game could be improved with shop system with the options to purchase better shields, weapons, lives and etc. rather than to wait for the power ups to cycle (very annoying)
Hmm... play easy setting, got 113K points but no badge. But it does not state the need difficulty... Nevermind, I will try "normal" difficulty again. Damn