Wow, this game is so underrrated! The animations for the flag, the fire, and the player's death are so smooth, I wasn't really expecting that! You should definitely add gifs to your screenshots, it would really help set your game apart since I feel like the moving aspect really helps your style come to life!
I really liked the slime buddy, how slime wasn't lethal but it was still useful to have the slime buddy to deal with it. I wish the other hazards were a bit more like that as well, rather than being lethal to anyone who doesn't match the color. Like for instance, what if the blue buddy was the only one who could sink in water, and everyone else floated? Or vice versa? And maybe instead of the electricity being a hazard the yellow buddy was the only one who could magnetize to electrical surfaces? I feel like the game's puzzles would be a lot more interesting if there was more distinction between the hazard types rather than them all just being lethal to anyone who doesn't match the color.
I also wish there was an indication in the playing area which slime you are selecting. Could be like an arrow or something over their head. I know it shows in the top left but it's annoying having to move my eyes back and forth. Also, I think it would be more natural for the buddies to be bound to numbers 1-4 rather than it being a cycling system.
Overall really great entry! It was a cool concept that was executed very well visually and gameplay wise