1. Added level difficulty selection
2. Add 4 optional difficulties (you need to clear the normal difficulty once to unlock)
3. Add a new super weapon "Blood Burst" Synthesis method: Scarlet Cross Lv8 + Blood Red Scattering Lv8
4. Weapon value balance adjustment
5. Adjusted the display order of characters and special effects. Prevent the situation that the characters cannot be clearly seen due to too many special effects in the later stage