Hello! I very much enjoyed the demo, and as such here are some things that can be improved:
-The initial instruction on how to equip items can be permanently skipped over, leaving the player without an instruction on how to equip the sword. If they didn't completely retain this information the first time around, this can lead to a lost player on the beginning area quite easily. A temporary sign of some sort that appears after collecting the sword but before destroying the rocks (that just brings up the instruction again) would be great.
-The fruit out in the background that is intended for the paper airplane takes you a bit too far back in the level if you don't make the jump. A checkpoint closer to that jump would be great.
-Spin Dash is a bit touchy. It can be hard to stop yourself after making your intended jump, leading to overshooting your target platform a bit too easily. Perhaps the ability to jump out of the dash to cancel it or some other similar approach would feel better as well as natural to utilize.
-The twisty trees can freak out when you strike your sword at them, but that's purely a technical glitch.
-More obvious signposting that lets the player know that there's not much else to the rainy area after the fruit would be great (you kind of have to figure out as such by spin dashing to the right until nothing's there, which I think is a death that can be avoided).
-Some invisible walls preventing the player from falling into the background when looking for the two bridge switches would be welcome.
-The effects of falling are based entirely on time spent in the air, but this can result in odd 'crushing' when the player is just caught on objects. Also, the player can get caught on objects, disallowing them movement and jumping ability. The player's vertical coordinate should be recorded whenever you leave the ground and checked against the resulting coordinate when they land to judge if the player should be crushed from the fall. If the player is falling long enough, check their vertical coordinate for about a second to make sure they're not caught on geometry, and if they are, respawn them. This can prevent softlocking should the player get caught on geometry.
-Allowing the D-Pad for menus would be welcome. I know controller support is in its infancy, but official PS4 controller support would be nice. By default it binds the Xbox buttons to incorrect locations on the PS4 pad, so its not too far-fetched to figure out PS4 support.
The demo was fun! I collected all the fruits and I'm going to be looking forward to this one! I hope these notes prove useful.