Good game, lacks upgrades

If you refuse to leave a stage, by gettign the key, but not leaving the door, you can farm money. Stay in the first few levels and get the maximum upgrades on a weapon and start on the armor. Then game is easy for a really long time. Eventually, there are no more upgrades to get and you have max gear, but the enemies get harder. Fro mthere it just gets boring

Sum owner of a new dragon about Colosseum, v1.12