I immediately fell in love with this game the moment I tried the demo. Excellent stuff! The level of polish, charm and detail is on a whole other level. It's clearly unfinished in some areas, but I can tell that this game will be something special once it's done. I have a few criticisms though... Well, first, just some bug reports:
1. I don't know what it is about the first bridge in the final level of the demo "Montes-3", but it seems very prone to bugs. On my first run all the Rangers fell through the floor and later, I had an incident where the green one got stuck on the edge of the slope, causing me to get softlocked since the others kept waiting for her.
2. I don't know if there are language settings? But the first tutorial started in english and abruptly swapped to spanish when the tutorial actually started. Then the rest of the game was in spanish. I'm bilingual so I didn't mind but it definitely felt like something was off.
With that out of the way, I do have some suggestions and complaints-- But keep in mind these are all out of how enamored I am with this game.
1. When the action gets frantic and there's a lot on screen, it's a bit hard to remember what button corresponds to each Ranger. It'd be really simple (and also good for color blind people!) if you had the cursor ring have the corresponding keys right next to the colored dots in translucent form, and then they could light up when you hold that key just as a minor cute gamefeel thing. It could even be an option so it can be disabled for those who get used to it and don't want the extra visual noise. 
I think it'd make the game far more accesible because as it is right now it's got a bit of a steep learning curve.
2. I think the time limits for these stages tend to err on the strict side. Consistently, I make it to the goal with only a few seconds left. It's a bit tense and exciting, yes, but it also means there's little room for error and it can make some levels very frustrating to do over and over. It also de-incentivizes utilizing the stop button, which in some circumstances felt like it was near mandatory because of how many things were onscreen at once (in the penultimate level, cramped tunnel setups with the enemy that shot projectiles and the crystal enemies at once). In general, I think this game would benefit a lot from having more lenient time limits across the board. Generally, with this kind of score-based games you want the act of beating the stage to be relatively simple so players feel motivated to say "Oh man, I could totally get a higher score than that!" and replay it-- I especially felt the bridge level was extremely tight and basically punished any small mistake so hard you'd run out right before the end. Making the timers more lenient would also lessen the frustration of the occasional messy setup where a lot goes on at once.
3. This is less of a complaint and more of a hope-- In the demo I thought the "melee hit" attack didn't add much to the game and felt rather shoehorned in. You don't even get much of a chance to use it in the next stage after its tutorial. Maybe I missed something but I felt the game already had a robust moveset otherwise. I hope in the final game there's bigger rewards to utilizing the melee attack (such as time bonuses or interacting with level gimmicks). In the bridge level for example I thought maybe utilizing the melee attack would allow Candy to still attack while holding wood or something, but that didn't seem to be the case. It just made the move feel more out of place.
To reiterate, besides these issues, I cannot understate just how impressed I am by this game's charm. The way the characters move, the little drawings at the end of the tutorials, and the gamefeel and music are all spectacular. I just felt like these things could be touched up to make it a far smoother experience. I'm rooting this game on! Keep up the good work!