I think that there are several areas for improving this game. The largest one being how the character moves. When he jumps, he should move like an arc, not teleporting up and then just falling. I recommend you check out Platformer Toolkit (https://gmtk.itch.io/platformer-toolkit) by Mark to get some ideas.
The horizontal movement doesn’t feel that good either. I suggest you having Diceman accelerate so it takes like a second to get up to full speed. Now he’s moving instantly, which makes him feel like he has no mass.
It’s also a bit too easy to die (no pun intended) in this game. You have no look ahead while moving, so all of the enemies seem to pop up from nowhere. You’ve already made the camera follow the player, so just make sure you increase how far you can be from the border before the camera starts moving.
Your game still has some strengths! You did a great job designing Diceman. He’s really cute! And I find it impressive that you did all the programming, music, graphics, writing, voice acting and design by yourself. Good job!