Mobile onboarding advice always says "don't dump all the features at once" — this simulator shows exactly why, as physics rather than opinion. A cohort of 40 synthetic users, each with their own working-memory capacity, moves through a five-screen onboarding flow while a leaky-bucket model tracks how much information each one is holding at any moment: load rises as new chunks are revealed and drains continuously as older chunks are forgotten. Turn progressive disclosure off to dump every screen's chunks in one instant burst and watch the same total content push more users over their capacity, spiking overload-driven drop-off and dragging comprehension down — then turn it back on, slow the pacing, or lower information density and watch the glass tank's average load fall back under the threshold ring as the cohort's activation rate recovers.