v4.01, v4.02 update

Please download v4.02; v4.01 is the version made for my friend who has spent a lot of time into this game

- Improved overall game balance

- Lowered some achievements' difficulty

- Added 1 secret achievement

- Since many achievements were modified, the achievement record of v4.00 and v4.01 does not compatible with v4.02 and later.

It does NOT mean the reset; the old record will still be there and can be viewed in legacy versions.

- The volume changer of BGM and SFX was divided

- Fixed 2 bugs (both in v4.01 and v4.02)