Plays well and the art is pretty well made, though if i'm being honest I don't see the connection to "only one". I might've missed something though :\
Viewing post in The Mortal Slime jam comments
That... explains a lot. I think i definitely just got super lucky at the beginning, which made me think "what's the point if i can just kill any slime"
One thing i would suggest is adding feedback to whether the right or wrong choice was made (perhaps some splash for the right slime, and dark puff of smoke for the wrong one)