The empty vials on this stage seem to mix with whatever is poured in and changes colors anyway.
The game is a really good idea, and making me do fractional conversions again is great.
Would you consider making it so that  the player has to take the potions off the shelf and read their label incase of look-alikes? 

Hmmm, I thought I had fixed that bug but clearly not! Having labels and stuff could work but I'm trying to keep the puzzles at the right level of complexity. Already I got a few folks who couldn't beat the first level.

Once I figured out what was going on with this, I didn't mind too much. It's not like I'm cleaning the bottles in between, so having residue that contaminates the sample isn't unreasonable. The puzzle is still solvable, but it should probably be consistent.