Great minimalist. I don't understand how come people are unable to go through it. The powerup system makes "hardcore" the easiest difficulty, since it provides bonus gold which in turn provides for stockpiling of powerups which makes ALL castle levels A BREEZE.
And I'm serious about it. Just find the secret alcove at level 2 (look around a bit) and spend all the bonus coins in powerups. They'll make the entire game absurdly easier - the timer is reason for almost ALL deaths in the game.
Also, the collision is very forgiving. I can see the cube going at least 2 tiles away from the path without losing it.
Overall, a great and challenging minimalist.