I just finished the game and it's excellent, although it was rather easy (or perhaps it's because I never touched the difficulty slider). I didn't encounter any bugs, but the battles got a little bit repetitive towards the end. I played a mage, mainly focusing on magic attribute (having it 35 at level 10) and putting my skill points on arcane and elemental trees. In battles all I had to do was spam earthquake-lightning bolt-inferno-boulder and then normal attacks. I never had to use any potions.
But overall, great flash game. 5/5
Protip: If you're tired to dodge the bullets against bosses, just move your cursor to where the boss is and wait. Bosses can't hurt you very well if you're under them but you still do the damage.