Rather repetative
But it looked nice. Random enemy spawns and a few bosses at the end of some levels makes a really boring game. But I admit it's graphics are decent. It wasn't challenging at all, just spam a few skills and you beat anything.
To improve, you could add a stat system every level up. For example you have strength for more damage, intellegence for more energy etc. Plus, the skill system was rather unbalanced where you had to put 5 points in the health regeneration to get to the next tier.
I also unlocked the secret character with the code axis. But I'm not sure if you have to beat the game to unlock him.
Overall a decent game. 7/10