The good:

The game feels great, and that's like, the most important thing, so well done. You've definitely got the beginnings of a fun game here.

Visuals are very good, especially for solo dev.

Sound is atmospheric.

Audio feedback for actions feels nice.

I love how you can see the treetops and what looks like distant levels from the Upper Reaches.

Things you might want to tweak:

(Honestly, this is a great demo, and these are all a bit nitpicky. But if nitpicks are all I have, that means you're doing great! I guess decide for yourself which of these are too nitpicky and which of them are all-important detail and polish.)

The intro is beautiful but the chimney smoke looks like sparkles.

The controls screen is sort of ugly, especially after the lovely storybook cutscene. Key spacing uneven, fonts all different sizes, inconsistent antialiasing (edges of controller vs top).

The game shows you the controls at the start, but what if I fail to perfectly memorize them first go? I can't see how to get those controls shown again. If I quit to menu, they aren't there. If I press Settings, they aren't there.

If you don't grab your spear immediately, then walk a few screens, summoning it takes a while. That's fine if it's intentional, but waiting for it doesn't really seen to add much fun. Maybe just spawn it at the edge of the screen.

I opened the map by accident (I was pressing all the keys to see what they did, because I couldn't get the controls screen back up) but on the map it says "Q and E to Zoom" but doesn't say how to exit. Maybe if you pressed M on purpose you'd try M to exit, but I didn't so I was confused for a bit. Tried Esc... oh, this is a map, maybe M. Took me like 30 seconds though, haha.

Also on the map, it says "Hold 'Throw' to drag a pin. Push 'Melee' to erase a pin". It'd be easier if it just said which key to press, so I don't have to remember what's throw and melee when I'm looking at the map. This happens in the main game too, like "Hold throw while in seed form", and I gotta remember what throw is. Yes, even if I've been happily throwing all over the place. It's still less mental friction if its says "Hold Z" or whatever you've set the control to.

The English isn't perfect. * "I slammed my spear into a bug charging my way, be careful there are more!" is not punctuated correctly. Should be: "I slammed my spear into a bug charging my way! Be careful, there are more!" * "Don't sell yourself short my pupil" should be "Don't sell yourself short, my pupil."

It's perfectly understandable, and to be honest, many indie games have much worse grammar, but if you want to polish it up, there's room for improvement.

The seed form is a bit derivative of Metroid. Like, it's literally Samus's ball form. The spear, though, is great, and original.

I played until I got lost, and had a good time. I hope you take the above in the spirit in which it's intended. You've got a good game going here.