As others have said, the visual approach is very idiosyncratic and vivid. Brilliant use of color to make something that stands out from the usual grimdark palette. Mapping these to a 3D environment works really well too, with the train providing plenty of excuse to provide billboarded assets with a nice parallax effect out the window. Lots of little tricks to suggest that you're experienced with how to create a convincing environment with visual effects.
I thought the idea was good! Sound design is always a great idea to base a game around., and the syringe and hulking passengers make such a strange but strong visual impression.The game really is contingent on having stereo headphones it seems - it can be a little tricky to make the right guess. Finding some variation in the gameplay loop could also help provide some variety: perhaps there are other elements involved in the deduction.
Nice work!