Thanks for the thorough information!
- I only tested the special attack on a dev version with infinite wealth, oops.
- There is no game over, but I forgot to enable checkpoints so it treats the beginning as a checkpoint, oops.
- I was afraid the ring staying on screen might happen XD (since the rings aren't well tracked in the code)
- For hitbox, maybe I can add a dark shadow around it to visually emphasize it.
- The only thing I know to do about the Linux version issue is to try compiling with a newer release of MonoGame.