Nitrogen is the nutrient that most often limits how much life an ecosystem can support, and it moves between four very different chemical forms before a plant can ever use it. This 2D counterpart renders the classic nitrogen-cycle box model as a flat flow diagram — atmospheric N₂, soil organic nitrogen, ammonium, nitrate and plant biomass — as five labeled pools whose fill level tracks a live set of coupled differential equations, connected by arrows carrying streams of particles whose speed and density scale with the real instantaneous flux, with a live stacked chart plotting every pool over simulated time underneath. Four sliders control the rate constants for fixation, ammonification, nitrification and denitrification, a fertilizer pulse button lets you inject a shot of ammonium the way a real application would, and live readouts track every pool plus the cumulative nitrogen lost back to the atmosphere through denitrification — and confirm that total nitrogen across all five pools never changes, only moves.