This really isn't my type of game, so I don't know how useful I can be but...

How to make it more immersive:
- I fully agree with LeviathanLaw's suggestions!
- Add some interactive points (e.g., a speed boost, attacks against opponents, etc.)
- When jumping over obstacles award players for the quality of their jump. Encourage player's to just barely clear obstacles as it will reward those who challenge themselves and encourage improving skills.
- Make each environment different for the player in someway (e.g., the snow level has ice that makes jumps longer, the desert level has quicksand that makes jump height lower)... I don't think messing with jump mechanics across an entire biome would be good as it would be frustrating to have to learn new timing each time, but little patches here and there would add some variety and make each area feel different.

I like the mix of 2D and 3D the visuals are great. It's pretty solid but I think it could use the introduction of a new mechanic to add more interesting gameplay. Adding a sound effect to jumping might be good along with some more monster noises for the things that chase you. I found it sometimes hard tell if an object was in my path or not, something visual to help with the perception of depth would be good I think. Also for some reason on the snow level it felt like my camera was lagging behind my character making it harder to anticipate things coming toward me, but idk if that was intentional or not

For immersion I would suggest improving the audio and adding more lively characters/environment models in the background, like two people standing having a chat, a moving windmill, etc

Nice work

The funniest game I've played on this Jam so far!