Really like the idea of playing a mimic.
You should indicate that left-mouse is attack.
I really like that whether you're hiding or not changes your music.
The enemies move around very randomly and rapidly, so it's hard to predict when they're vulnerable to attack.
Repeatedly disguising and dashing seems to be the whole game, and there's no reason to move into a room. I just wait in a doorway in disguise until a guy gets close and then I dash + attack. The repetition gets dull quickly.
It would be more interesting if there were environmental features you could use to your advantage so there's a reason to move around, or perhaps items to find that help you. Maybe there could be hazards in the rooms that you can lure the enemies into when in disguise, like acidic slime, spike traps, poison spores, steam vents. Maybe you can explore to collect and place hazards.
One interesting feature of D&D mimics is their adhesive touch. Maybe the mimic's attack can stop or slow enemy movement, so that environmental hazards can kill more easily.