I appreciated the attention to detail in the art design. Game has clear aesthetic identity. I liked the enemy design too, especially the ghost. Here are some suggestions:
The jump could be improved. The floaty jump make some sections unnecessarily difficult. For example, because skeleton arrows travel a lot faster than the character falls, I found myself routinely "trapped" in the air. I also found myself wishing a little tap on the jump key would correspond with a little jump.
I think certain design choices hold back the gameplay a little bit. Here are two examples: The ladders are pretty slow and not very exciting. At times they frustrating, as when you automatically grab one while jumping and suspend yourself midair right in the path of an oncoming arrow. The fire breathers looked really cool but the timing was unnecessarily difficult because of the long fire duration and floaty jump.
Overall I think this a pretty good effort and could be quite enjoyable with some adjustments.