Better art, better fighting

Big quality change in the background, chose a brighter look and more parallax layers.

This will be the outside setting, and the main exploration/playing will be inside a towering building.

Also:
 - the health bar works now
 - the skeleton does damage to you when you just walk into it
 - death/respawn when health runs out

Some wonky stuff happens if you jump into the mob, because I haven't handled airborne collisions yet. I'll be able to knock that out quickly.

I also added a debug feature to press Left Bumper or F1 to restart the level.

Bonus feature on this build just because I was messing around: 20 double jumps

Still motivated, still chugging along!

Thanks to everyone who is following along and providing feedback.