Hi!
The king should have been behind the door, which is the final boss of the level but seeing the comments I'm starting to think that I uploaded a version with a broken boss, or at least with a boss who doesn't pop the credits when he dies.
I intend to continue developing the game, I want to add monsters but helping the adventurer and more type of wards with different abilities like archers or I don't know ninjas perhaps.
I will certainly add the coins and the damage dealed markers on my To do list.
Thank you for your comment!