I agree that the art style is great, definitely a strong point.
The platforming is a good challenge too, the dashing feels very rewarding when you get it right and just plain fun even when you don't. Though once I came to where wood was introduced I became aware of just how frustrating it was that other stone platforms didn't work in the one-way manner wood did. Wood is the best platform, change my mind.
I only have two major gripes with the game - the first is the enemies. They take a good few hits to defeat, which wouldn't be as big of an issue if they weren't so efficient at depleting your health. A single enemy can shoot me three times before I manage to kill it, so finding another a short ways down the track can kill me immediately without giving me a fighting chance. It's frustrating and makes them feel more road-blocky than they deserve to be.
Finally, the notion of absorbing souls to get stronger is great, but it wasn't expressed strongly enough to feel like a 'core force' of the game, even though it is. Finding a new soul feels more like a classic "obtaining a new skill" moment than joining forces with other souls to become stronger. This wouldn't have been so noticeable if it weren't for - in addition to the theme of the jam influencing my interpretation - the death screen reinforcing the notion of 'together'.
At the moment it doesn't feel like there's anyone to be 'together' with, which is frustrating if only in the sense that I know contextually there is, it just isn't reinforced enough in-universe. I really like the concept of working together with other souls, I think it's a great aspect of the game that deserves buffing up. I think a bit more work on this could really make that element shine and I'd really love to see it!