Updated key sprites
Added more texture variety to maps 6 and 9
Made silver spider enemy have more health and speed.

Added Y axis only invert
Fixed audio menu bottom slightly raised

Larger explosions for barrels
Added mouse invert controls
Made mouse sensitivity settings save better
Added more textures to level 2
Various map fixes
Player starts with a little of every ammo type
Louder explosion sounds
Added explosion sound to barrels

Made all boss mechs a little harder.
Changed last Boss fight to make it more interesting.
Hit boxes are larger for pickups.
Fixed no floor on first large elevator.
Added a continue screen upon death instead of returning to the main Menu.
Various other map fixes

I plan on trying to find a way to make invert look work over the weekend.