Your game reminded me of the old disney games for genesis, but only I could hardly deal any damage to the first boss. Other than that it looked good, thanks for making it.

I did get the concept, unfortunately, that was inconsistent for me. You've built the atmosphere, but suddenly you change it on the second and third. It would be better if you stuck to an art style and mechanic with different bosses who had their own unique skills.

You also need to improve the way the player moves and attacks (in the first fight). It's pretty uncommon to use the left button to attack in this kind of game. The acceleration was a bit slow compared to the animation speed.

I hope my comment can help you grow. Good luck!

It's pretty much three games packed into one. 

The first boss is cheeseable by just staying right in front of him, his slash attack and laser attack don't hit directly in front of him. The player hurt animation play after the slash animation if the player gets hit during the slash animation.

The second boss felt frustrating to fight. Since you can only attack after a long cooldown and if you're going to have penalty for leaving the screen, please don't use attacks that eat almost the entirety of your screen. (Still winable though)  Music is a bit too chill in my opinion.

The third boss is... I don't know. I didn't get to see the third brother. Felt the invisibility frame was too short for the dash. Why is it so blurry?

There is no sound effect when you fight the bosses. It would be great to at least have hit feedback sound effect.

Edit : Forgot to write about the practice mode. It's really good to have that in the game, so everyone can at least experience every boss. Great addition.

Good job on the game.

A great boss rush game. But the hitbox is kinda weird and you should add some sound effects to attacking.

Interesting idea about beating only the bosses, but I can't beat even the first one because I can't reach the back of the boss to deal more damage to him.

I like that your menus are so well fleshed out, they look good and convey a lot of information. I felt that attacking was alittle sluggish, increasing the animation speed might help with that. Also, try seeing if you can play with the gravity to help the jumps feel less floaty. You can do this fairly easy if you are using a rigidbody2D component on your character controller.  Doing this will cause you to have to increase your jumping force, but it should feel pretty good to play.   I love the boss rush concept you have here.  Good job.

A bit too difficult for me, but that's due to me being rubbish at these sorts of games. I couldn't beat any of the bosses but I did go through the practice mode to see them all. As mentioned in other comments, it could really do with some sound effects, but I did enjoy the music. I liked that the 3 bosses are essentially 3 different games with completely different mechanics. Good job!

easy to understand and pretty fun. Just need some sfx in the game. I think SFX in this type of game is really important to build the vibe too. Overall good job for completing the game!

A neat boss rush, I do wish there was sound effect for hitting and getting hit by attacks. Also My hatred for falling off the ledge and immediately dyeing continued to grow on the first level. You could punish the player with health loss, but if you are going for the hard core crowd i can't complain. Well Done! 

Whoo what a unique game taking on bosses right away. I like the soundtrack that went with the bosses. The drake one felt like one of those classic side scrolling airplane game at an arcade.  Just I had a bit of trouble with that one as couldn't figure out what the hand with pointer appear meant.  For the dark soul boss, i feel the swordsman you control attack could have been just a bit faster. Just my opinon. Very interesting game you have set up here :)