A few things you could improve on:
Allow only one item in a mortar at a time. Might also look into how to handle the pestle better, having it in your inventory is kind of weird, you can't just put it back either.
Using the cliffs from the coal/sulfur mining site you can go past the invisible walls/rocks at the lake and furtheron jump off the island and fall forever (until everything turns grey.)
Could turn out to be petty interesting, if you add some more content :D