The gameplay loop is fun and quite addictive in the early levels. Despite the minimalist style there's a lot of little visual touches, like the blue circle getting more transparent as it stretches out then shaking as it nears the limit. Getting the last couple of circles for your limit is very satisfying. I think there should be a requirement to get to within 3% or so of the capacity before you can turn mass into experience.
The gameplay can absolutely be the core of a horny game, but then something else needs to happen for it to be arousing. Maybe the circles you collect could be little people and they lose their clothes when you expel them, or maybe there could be a character that poses suggestively as you gain levels.