This game was fun and felt like the start of something great. I like the art style, the relatively small character, the recoil effect, and the hostage release concept. I never did find any secrets, sadly :).
I thought I was softlocked on the second board: when I tried to activate the final blue screen (alongside my hostage), nothing happened. I started the game over, but the second time around I ended up in the same situation, kept trying the blue screen, and one of the times it activated and gave me the portal to the boss. I wondered if perhaps the hostage needs to be right on top of the blue screen, too? Making that mechanism less exacting would probably have solved my confusion.
But that experience made me expect that part of the puzzle here was going to be finding a different path out, taking into account a non-jumping character who follows you. E.g., the hostage might need to be led in one way, and then the player might need to shift to a different path to then guide the character in an opposite direction, down an elevator, etc., avoiding harm to the hostage all the while -- it feels like a puzzle-rich concept that you could really develop.
Nice work!