So, played through the content and have some thoughts.
1. Would love to see some sort of accessibility/difficulty adjustment added eventually. I love the art style and character designs in this game, but this sort of gameplay is not my typical jam. I would like to be able to play through an easier version of the fights so I can enjoy the story and characters without getting frustrated with learning every minutia of the bosses. To the same, but opposite end, this would give those that love difficult platform bosses a way to increase the difficulty of the fights. I would say, keep these in mind as you develop the game and try to include ways to be able to add them in.
2. It is clear that Petra is going to be a very important character later on in the story, possibly a final boss even. I would suggest not just leaving her in the void of the opening scene, otherwise the player may forget who she is.
3. An auto condense button for inventory would be nice. Right now it seems like you need to manually condense items down.
4. I am curious how much of the story is already figured out.
5. Some sort of "Compass" would be nice once the game is more fleshed out. Similar to in Legend of Zelda where you get a map to show the layout of the game and a separate compass that shows where important items or possible boss fights are.
6. A way to refight boss battles without restarting the game. As you collect items and get stronger, being able to go back and try out new gear and skills against old bosses would be nice.
7. At no point was there a tutorial on how to open the inventory or how to dodge roll. Both would be good to add early on, even if it seems obvious. Just a quick pop up saying "Hey, dodge roll with j. Open inventory with i."