Hi!

Finished the demo and I'd say that overall it was a good experience. I took some notes during the process but do keep in mind they're not in any "priority" order:

1 - Combat feels rather sluggish. The hitboxes seem to be bigger than they look at times, and the reach of the attacks is rather limited, so when fighting regular/smaller enemies, you very often end up tanking a hit in the process. It is much more noticeable in flying enemies. The hitbox dissonance can also be noticeable on the first boss, when it seems our character should be able to fit in the gap between two falling blocks but gets hit regardless.

2- Regarding flying enemies and thus mid-air attacks, I personally find it a bit confusing you can't continue the combo as soon as your height drops. What I mean is, maybe you jump, start your first attack and notice you missed, and you'd expect to wait until you fall a bit lower to continue your combo. However, the combo just can't be continued after we interrupt it, so I ended up avoiding fighting most flying enemies for this reason.

3 - Character design and backgrounds are endearing, and the music suits the game nicely and it feels immersive.

4 - I feel that sometimes the player character can be difficult to see depending on the background, I'm not sure if a more "zoomed-in" view could help with this or giving the player some features that an ensure it always stands out.

5 - Zones don't stand out much from each other. Although background changes and the 2nd zone has some slightly enemies, they don't feel "themed" enough. Perhaps enemies more exclusive and reflective of the ecosystem we'd expect to find on zone 1, and a different set of enemis also fitting the theme of zone 2 (plants, bees, more "wildlife-y" ) could be nice.

6 - Definitely a minor quip, but it could be nice to be able to heal back at checkpoints. Sometimes we're too hurt and have no energy and we're right at a checkpoint, so to "refuel" it's sometimes better to just let our character die just to respawn, so being able to heal at a checkpoint might help optimize it, even if at the expense of respawning the enemies.

7 - Character movement feels nice and responsive. 

8 - Platforming felt a bit mixed sometimes. I'm used to platforming with platforms that don't have collision on the bottom so I might be biased. Sometimes I feel platforms are a bit narrow, or too close to the ceiling, and that combined with the fact that sometimes it can be hard to adjust the distance of our dash, can make it as if some specific sections are more complicated than they should.

8 - Minor quip, but if boss fights get more complex in the full game, an option to skip cutscenes would be welcome, in case someone has to try a boss 20 times but have to sit through a cutscene every time.

9 - The bosses themselves felt fun, although the combat sometimes felt a bit long, especially on the reaper. There's few attack patterns and they don't get mixed up, so sometimes it feels like more of a memory game than us learning the moves and adapting to whichever one the boss decides to toss at us.

10 - The usage of lava/fire feels a bit inconsistent. With fire form, we can walk on lava. Also shortly after acquiring it, we get on a platform that goes up and we go through some horizontal flame pillars without problem. However, when it comes to vertical pillars, we have to dash through them no matter what. Moreover, any mistake on that front is an insta-kill, which feels frustrating.

11-  On the subject of death and insta-kills, it's good that we can respawn very quickly and the spread of the checkpoints feels reasonably fair.

12 - It is confusing why some things persist through death and some others don't: pressed buttons persist, but levers and doors don't. This also makes it so revisiting an area to explore it when we have new upgrades feels less appealing, since it feels that we have to "replay through most of it again".

13 - Minor quip, on the subject of buttons, it's a bit weird we have to press a key to press them when some of them are on walls and our main attack is very explicitly a punch. I think either allowing punches to activate them (we allow fire blasts for the levers, after all), or making the buttons a different "thing" so it has to be interacted with no matter what, would make more sense. Turning the buttons into a computer similar to the one that has the map, for example, but with different features.

14 - Shop items and upgrades found in the world don't feel too exciting (aside of the new forms we get, which are mandatory upgrades). Aside of stat boosts, it could be different stuff such as longer reach, additional hits in the combo chain, projectiles for the other forms, increasing the amount of projectiles fired, hurting enemies back if they hit us, seeing all the upgrades in the map or being able to manually mark them, etc.  There were areas where I knew I saw an HP boost but didn't bother to go all the way back to that preivous area to get it (once I had double jump), but if instead it was a mysterious icon for an upgrade I can't quite guess, it might keep the player curious enough to really want to revisit that section of the map to finally find out what it was.

15 - Not sure how I feel about the map not showing the player (could also be an upgrade!). On the one hand, it can be interesting to be made to look at your surroundings and comparing with the map to figure out where you are. On the other hand, metroidvanias can end up having rather complex maps so it's nice to know where you are. Even if not the exact position, just knowing which "room" you're in can be quite helpful.

16 - Needing energy for some traversal (fire blast to hit a lever, null punch to break a wall, etc) didn't feel too good. Sometimes we went through a platform section only to find out we have the tools to traverse but we don't have the energy for it nor any enemies nearby to recharge. 

Also, couple of minor bugs I found, but nothing game breaking:

1 - On zone 2, when we encounter nina the shopkeep, during the conversation the name and the portrait get mixed (at one point nina is speaking but the name has changed to "player")

2 - On the cutscene for reaper, at one point instead of showing the "portrait" for our player, our full body is shown (when saying "show some respect!")

3 - This one bothered me a bit more. In zone 2, in an area of the map above the character Char (shortly after we get the punch for the Null form), there is a boxes and buttons puzzle that eventually leads us to one of those jars with crystals, but behind a wall. Turns out I didn't have enough energy for it, so I went back to find an enemy to punch. After I had enough energy, I wanted to go back to that section but I no longer could, since one of the doors would always remain closed. I had to die to reset the puzzle back to initial state to get to that crystals cache.

So I believe I finished what has been done so far and I think it's a good start. Here are some notes/thoughts I've had while going through it:

1. The art direction is really good! I did notice that it's hard to track the PC if you're in the starter form on the second stage. Other than that, each form is unique, varied, and nice to look at. I wish the first form's color would change to like a light green (mint perhaps?) for some visual difference.

2. From playing the game, it never felt quite right to get a double jump until the end of the game. It might feel better for each form to have it and for the air form to have potentially a triple jump and/or a second air dash to give it some unique qualities.

3. The three-hit combo feels rather sluggish and slow, and having barely any hit-stun on the three-hit combo does not feel good. Often times, I get hit when I'm attacking mobile enemies when I try to recover energy. Either the enemies keep on coming or they get knocked away before I can finish the combo.

4. Having a small amount of energy regeneration when it comes to level traversal can go a long way. I found myself nearly soft-locked when I ran around looking for enemies to get energy to open up doors with fireballs or the E ability in the first form. 

5. I'm not going to go too far into the story since there isn't much to work with, but it didn't keep my attention. Lore is nice to have, but my drive to learn more about the world feels hampered. Plus I liked the little rabbit guy and would have been nice to see them staying around longer.

6. The bosses in the demo are fun, but there are bits of them I want to address: the character hitbox is too big to dodge the bricks falling down in the first fight. Often times, I would try to fit through the smaller cracks thinking I could fit if I managed to aim it right, but I'd always get hit and it didn't feel great. The second fight with the robot vulture (I think it's a vulture anyway) is better, but having the boss dive from the sides of the stage felt strange to have to dodge. Plus, the tornado attack needs to have either a form of windup or a visual tell so the player knows it's coming. It's not the end of the world, but it would feel better if the player could get a quick visual cue to react to a mechanic that's mandatory to damage the boss.

Overall, good start and I'd love to see if/where this goes in the future!