Pick a scenario; the sliders stay editable.
Flat above the lower critical temperature (25 °C, thermoneutral zone), rising linearly below it. The dot is the current room.
Play with the swing to see the angle trace.
The science
Energy budget. Basal metabolic rate of non-passerine birds follows the allometric law BMR = 78.3 M0.723 kcal/day (M in kg; Lasiewski and Dawson, 1967), i.e. about 328 kJ/day for a 1 kg bird. The day’s cost is BMR times an activity factor (sleep 0.9, rest 1.2, perching 1.5, eating 1.6, social 2.2, training 2.4, play 3.2, flying 8; typical, simplified) plus a cold surcharge. Hunger in the HUD is the filled fraction of an energy reserve (crop plus fat) that holds Emax = 1.6 BMR, one day of perching.
Thermoregulation. Scholander–Irving: inside the thermoneutral zone (above Tlc = 25 °C, assumed) the metabolic rate equals BMR; below it M = C (Tb − Ta) with C = BMR / (Tb − Tlc) and Tb = 40 °C. At 10 °C the bird burns twice its BMR. Food energy: seeds 22, pellets 14.5, fruit 2.6 kJ/g (typical values; portions 8, 12 and 35 g).
Needs. Stamina falls with activity and recovers while resting or asleep (22:00–06:00); social, cage hygiene, water freshness and fun decay with time; health relaxes towards a target built from satiety, hygiene, water, diet balance (a seed-only diet lowers it) and comfort; happiness relaxes towards a weighted mean of the needs plus a small enrichment bonus per decoration. These weights and rates are game-design choices, not measurements.
Training. Each successful session closes a fraction α = 0.08 of the remaining gap to full skill, so after n successes s = 100 (1 − (1 − α)n), an exponential learning curve; a failure closes 20 % of that, and skill slowly decays (forgetting). The success chance grows with stamina.
Swing. A bird on a swing of length L=0.85 m is a physical pendulum, θ″ = −(g/L) sin θ − cθ′, integrated with RK4 at 1 ms; the small-angle period is 2π√(L/g) = 1.85 s and grows with amplitude as T0(1 + θ0²/16 + 11θ0&sup4;/3072).
Checks. (1) BMR scaling; (2) a 12-hour simulated cold day against the closed-form bill; (3) the learning curve against 1−(1−α)n; (4) the RK4 swing period against the series; (5) a 1440-step day returning to the same clock time; (6) eating then resting conserves energy. Simplifications: one bird, no illness, no moulting or breeding, the macaw is a 1 kg blue-and-gold type, wings fold rigidly, prices and rewards are illustrative game numbers. Real parrots need daily out-of-cage time, varied food and company; this is a model for learning, not a care manual.
The aviary, perches, toys and both parrots are models made in Blender; the model and the game logic run in the page.