Senescent cells don't just sit still — they broadcast. This 2D canvas simulator models a sheet of tissue as a grid of cells sitting on a diffusing field of senescence-associated secretory phenotype (SASP) factors: when a cell becomes senescent it starts secreting into the field, and healthy neighbours bathed in high enough local SASP concentration have a rising probability of themselves being pushed into senescence — the paracrine "bystander effect" that lets a handful of stressed cells seed an expanding patch of ageing tissue. Click any healthy cell to trigger it into senescence and watch a new secretion source spread outward through the coupled diffusion and conversion dynamics. Immune clearance constantly removes senescent cells in the background, and a senolytic-dose toggle lets you see what happens when that clearance is selectively boosted.