Love it. Background parallax was pretty solid, though it could have used more layers and such. I like how you've tied it in to your previous games. I could easily see this as the intro to a much longer witch platformer/bullet hell game.
Not too sure about the platformer mixed with bullet hell mechanics, at least in confined areas like train cars. You had objects to jump on in the first couple cars, but not so much after that (Which is where it was really needed).
In the boss fight you gave the player a broom, but it was actually kind of hard for me to notice -- in part because there wasn't a lot of room to move in the first place. You did try to communicate it via the other witch on the broom, but I think you could have had a train car just for picking up the broom that leads into the boss fight. Like a storage car for all the witches' luggage, and there's a place for all the brooms. Once I realized that I could fly, the boss fight wasn't all that bad -- just sat on the right side of the screen and killed the rapid fire enemy first.
Also, on the description and the ingame controls, you say right mouse to fire, but it's left mouse.