This is an excellent game!
My favorite part, and maybe one of my favorite mechanics in any of the games I've played so far, is the teleport to the other side of the block- this is absolutely brilliant and really expands the possibility for high-level gameplay.
I'm not sure why I would ever choose to not sprint, if anything I think it would maybe be better if the player always moved at the faster rate and could press shift to slow down temporarily for greater precision. Maybe that's just me though. Same goes for parrying; I'm not sure why I would want to make the fireballs go faster since they are harder to avoid after. I think having a health bar or timer on the fireballs to know when they will run out would help inform decision-making for whether or not to parry.
Overall, this is a really good game, and I can see myself playing it more when the jam is over. Nice work!