A few suggestions
The game is pretty good, but there are a few things that I do not like.
1. It is taking way too long to level up after you reach level 4. It is annoying because you cannot get to the last boss until you are level 6. Personally, I lost my interest when I had go back to level 3 in order to get enough exp points.
2. After I finally beat the Advanture mode, I expected something awesome to happen in the arcade mode, but no...the arcade mode is just boring and repetitive.
3. The final boss is way too easy, he hardly touched me in the fight. It makes nonsense that the second boss is way tougher. Also, walking around for 5 minutes just to find a key with every enemy dead is not fun. Make more action!
I hope that you follow my suggestions and make some improvements. The game is good, but I have seen better.