v0.18.19 Updata - More challenges and optimizations.

Game-Related

• Master difficulty unlocked.
• Monkey difficulty unlocked.
• Difficulty selection UI updated.
• New elite enemies may appear on difficulties above hard.
• When enemies die, there is now a brief corpse residue effect.
• More types of minions are now available.
• New music plays when elite enemies appear.

Balance Adjustments

• Lightwave: Maximum bounce bullet damage is 200.
• Saint: Base revival count +1, when enhancing, revival count increases by +1.
• Plan Perfection: Increase in experience points by +40%.
• Track Master: Increase in damage ignore by +15%.
• Stress Resistance: Increase in range by +40%.
• Revival count research purchase price adjusted to 10,000, 20,000.

Fix

• Remade some animation logic to avoid screen errors during upgrades.
• Performance optimization.