Neat game. Usage of Jam theme is on point. I liked your choice of music too, somehow captures the feeling of embarking on an epic quest and a heaviness which matches the feel of the controls. Nailed the core feel of the sword movement.
For improvments, I'd strongly suggest implementing DJdevil8's suggestions for not holding the mouse button and having a boost cooldown/availability indicator. I'd also suggest adding a mouse sensitivity slider to account for different people's mouses.
Nice one!