I had fun with this!
Great job working with the limitations of the Game Boy!
The art and level design worked pretty well!
I got the "Coward Ending" and the "True Ending" ..also I was killed once
For constructive criticism, I think the player felt just a little too slow. Speeding things along would have better enticed me to try to get all the endings. That's really cool how you put the ending counter on the title screen though!
As a whole I think The Lab does a great job of fitting the theme and spooky vibe. Overall it works well as a horror game and I could see a longer more polished version doing well! Definitely something to be proud of!