Perhaps try doing some more bracketing to get more definition to the snail. As it is it's having a hard time looking three dimentional because of the brightness of the white.
I'm not sure that this works for me: sure, it absolutely meets the challenge description - but it isn't within the spirit of minimalism for me - it wasn't as simple as all this, I don't think; it isn't absence of information, rather the precise control of very limited, but nevertheless very important, information - yur big high-key background is simply a photographic nothingness. Accomplished shooting, doubtless, but ...
Good focus on the snail. The detail is clear and I like the shadow below the snail....but it can get kind of hard to look at a pure white background. Perhaps something ivory, yellow, beige...anything....might improve the score a bit.
Not bad. I could wish for a bit more color on the snail shell to liven it up, but at least the shadow gives some meaning to the the pure-color background. I wish it hadn't been pure white, though, since the result is harsh on the eyes and hard to look at. Next time snail on parchment?