This 2D companion uses the exact same accounting as the 3D scene, viewed top-down as a flat ring instead of an orbiting camera. Each year the biosphere regenerates a fixed budget of resources — its biocapacity. Humanity's ecological footprint is the demand placed on that budget across six accounting categories: carbon uptake, cropland, grazing land, forest products, built-up land, and fishing grounds. The ratio between the two is the number of "Earths" required:
Earths demanded = Σ categoryDemand_i (i = 1..6)
Overshoot Day = 365 × (1 / Earths demanded)
Days in ecological debt = 365 − Overshoot Day
If demand stayed at exactly 1.0 Earths, the budget would last the full 365 days and there would be no overshoot. At the real-world 2024 figure of ≈1.75 Earths, humanity exhausts a year's regenerative budget by late July and spends the rest of the year drawing down natural capital — depleting fish stocks, shrinking forests, and letting CO₂ accumulate faster than ecosystems can absorb it.
- Category buttons + slider — edit any of the six demand components; its bar around the ring and the total recompute live.
- Ring of 365 markers — one per calendar day. Markers before Overshoot Day glow green (within budget); markers after turn red (ecological debt).
- Play year — sweeps a marker around the ring at the chosen speed; a red debt halo grows around the central Earth disc once the sweep passes Overshoot Day.
Real-world relevance: this is the exact accounting logic the Global Footprint Network uses to publish Earth Overshoot Day every year (July 25 in 2024, and creeping earlier most years since the metric began in 1971 near December 31). Drag to pan the ring view and scroll/pinch to zoom.