It seems really difficult to get the upper hand on the first couple enemies. They always notice you as you approach and when they notice you they're invincible for what feels like forever, and you have to back off and wait, but not back off so far that they lose track of you, because then they'll notice you and become invincible again when you approach.
Configurable controls are a must, too. Spacebar to jump and Z to punch feels really messed up. Make it Z to jump and X to punch at least.
