Semi-on-the-fly comments:

1. Controls are QWERTY-only instead of layout-independent, BUT arrow keys are enabled, although without strafing.
2. I like our magical staff. :)
   The enemies are super cute! :) And you managed to animate them.
   And I like the valleys too, with the ‘squary’ shadow near the top. :)
   I also like the way the die is shown rolling. (By the way, a coloured die instead of a numbered one is original.)
3. I think there should be some limiting mechanic against shooting, because otherwise, you can just hold the left mouse button constantly.
4. Is there some difference between the different types of enemies, such as health? I did not notice.
   Ah, maybe in speed! Reds seem quicker (while I am going back, they seem to go at about the same speed as me).
   I agree with ArmedChair and RabbitDev that some variety in enemy behaviour would have helped, because each colour more unique, with a different playstyle.
5. Ah, managed to have the enemies slide on the slopes while I was descending! :)
   Bug: the purple enemies stay stuck there !
   
   Then some were stuck at the bottom on the floor, again, so it may be because of the slope.
   
6. I notice the clouds now; also cute to see how they are elongated. :)

The visuals are a nice base and go well with the colour-changing concept! I just wish there was more variety in gameplay, including both enemy behaviour and how we can act (shooting).

Otherwise, super cute; do not hesitate to reuse your graphics and idea.

Would be helpful if you included a web build!