Roses 'N' Guns Update

I've been working on an update to Petal to the Metal dubbed Roses 'N' Guns, adding in a new gun and audio overhaul as well as credits. Change notes are as of below.

CHANGE NOTES:

- Gameplay change: Gun upgrades no longer revert backwards at all due to
death now resulting in immediate Game Over. The reason for this is that a
respawn mechanic no longer made sense with the previous gameplay, and reverting gun upgrades was found to be frustrating. Hopefully taking this element from  roguelikes improves gameplay

- New gun added, last upgrade changed: The last upgrade was found to be unsatisfying to players so it has been replaced with a more powerful gun that fires a different type of ammo, as well as increased laser damage

- Sheriff 'Death' animation changed: critique showed that the old animation took too long to indicate to players that the enemy had been killed and was dying. New animation is quicker and more obvious, as well as keeps with the 'blinking' out theme of the tank and dog

Audio Overhaul: A much needed audio update to most parts of the game, as listed below:
- Gun Upgrade
- Player Regains Health
- Player Takes Damage
- Objective Active
- Objective Paused
- Bombbaby Enemy Explosion

Added: 
- Credits
- Second Epilepsy Warning
- Transitions
- Invincibility indicator during Objective Completion
- Studio Splash Screen
- Progress Bar UI updated
- Kinetic Bombardment sprite updated
- Tutorial only shows up once, not after every death

Increased:
- Higher Chance of Healthdrops (100% for Jellyfish)
- Time between Waves
- Boss changes phases earlier

Decreased: 
- Sheriff Health to 1
- Shotgundog Health
- Bombbaby Health
- Amount of Kills needed per Upgrade

Removed:
- Rainbow Mushroom Drops
- Combo
- Nuke Detonation Upgrade reset in final upgrade
- Lives during Boss

BUGS FIXED:

- Final upgrade Laser width
- Singleton Pattern on leaving game running
- Main Menu frame drops
- ESC key pauses but doesn't unpause
- Music Audio transition from Boss to Credits, or Boss to Menu upon Death
- Can pause and unpause during tutorial causing game to run in background