Turning real questions into mathematics and checking the answer: the modeling cycle and dimensional analysis (units, the Buckingham-pi idea, sanity-checking equations by units), rate/compartment models with exponential and logistic growth, optimization modeling (setting up and solving a real max/min such as the minimal-cost can), discrete difference-equation models and their equilibria, the stability of fixed points (whether a perturbation is damped or amplified), and model validation with residuals, over-fitting, and parameter sensitivity.
Free to start · adaptive placement finds your level · reviews timed to your own forgetting.
Every idea is taught with motivation and a worked example before the drills, and an FSRS spaced-repetition engine schedules each review for the day its model predicts you would forget it. A short placement check finds what you already know, so you start Mathematical Modeling exactly where it's useful.