Congrats on making your first ever game jam. Since you asked for feedback, here's a couple notes :)

• A like the jump sound effect, it complements the pixel art style! It would have been nice to have a sound for when you take damage, too (I didn't realize I was taking damage at first)
• Nothing happened for me when I merged with the flub in the top right corner
• Maybe I took damage from the boss too quickly, but I couldn't beat it with just the starting attack (or I gave up after several seconds)
• I liked the changing weapon abilities with the colors!
  
  
  

First off, congrats on making your first Game Jam!

You asked for all feedback possible, so here I go.

The game is quite short, but for a first game (and alone) it's impressive you already were able to do all of this in 2 days.

Visually, it's simple yet pretty clear: We know what is an enemy, what is a power-up and what is a platform. The red dots that damage you at the start might need a bit of change in some way though, I thought that they could be destroyed by hitting them, but I ended up taking damage instead. Nevertheless, props to the fact that you added the boss' blinking when it gets damaged, it helps with clarity.

Since you used Unity, make sure to have the Boss' music loop onto itself in the Audio Source (there's a checkbox for it). I outlasted it with my first battle (I tried to fight it without any power-up because I lost it before the fight and didn't know there was a bossfight there) and the void is a bit weird. It's a simple change that makes a lot of difference!!

The powers are diverse, inventive and pretty clear to understand, so props to you for that! Though I feel like adding something to represent a cooldown (character blink / charging bar / color change / sound effect / etc...) could add a lot. I spent a majority of the battle spamming my mouse button because I didn't know when I could attack again.

For polishing, adding a small picture in the "Win" screen, a pause menu, the character looking the other way when moving to the left, or a main menu could add A LOT to the game's feel. Some invincibility frames could've been welcome, and/or something to telegraph the boss' attacks before they hit you once. After seing them we can clearly know which attack is coming thanks to which leg is moving (that's a nice touch though, thank you for that), but it feels like you have to get hit the first time since you don't know the area it'll affect... Maybe some semi-transparent overlay right before it hits to know? it's just an idea though.

Also, maybe adding some pictures, or more presentation in your itch.io page might help people want to play more of your game (I know that it's a tough UI to understand how to setup the page, don't worry it'll come with time).

Overall, some good ideas for a first game, there is progress left but with what you did there, I have no doubt that you will be able to do even better next time!
Congrats for your submission and good luck for next times!