Attacks

- Added a new attack, "dspec_earth_wall".

Stages

- "Smiley Floats" is now on the default stage select (and "stage_choose_random") instead of "Battlefield"

Fixes

- Perfect shielding now works again.

Extra

- Removed blank folders from the project, and fixed filename capitalization inconsistencies.

- Updated comments to be more consistent for the documentation.

- Updated copyrights to 2023.