Fruit of Preterition

Motivation: How much caffeine is still in your body when you go to bed? And how does that change if you swap one big morning coffee for two smaller ones? The shape of the answer is a saturating-then-decaying curve, and the parameters are a few half-lives and one body-weight scaling.

Background: One-compartment pharmacokinetics with first-order absorption. The model is a textbook in two equations; the interesting bits are the timing decisions you make on top of it.