This interactive Pomodoro timer couples a classic focus-and-break clock with a simplified cognitive model. As the accelerated session runs (one real second represents one simulated minute), it estimates how your focus score, stress-related cortisol and energy rise and fall across cycles. The focus curve blends an ultradian wave that peaks roughly every 90 minutes, a slow daily fatigue term, and a bonus that grows with each completed pomodoro, giving an intuitive picture of why short, structured breaks help sustain attention.
A circular countdown ring, eight pomodoro markers, and three live traces for focus, cortisol and energy. Focus is modelled as 0.75 plus a sinusoidal ultradian boost (90-minute period), minus a daily fatigue term, plus a bonus of up to 0.3 from completed pomodoros. Cortisol climbs during focus phases and eases during breaks; energy falls with fatigue and high cortisol.
Pick a mode button — Pomodoro 25/5, Deep 90/20 or Sprint 15/3 — to set focus and break lengths. Press Start to run the accelerated clock, Pause to hold, and Reset All to clear counts and curves. Watch the side panel for completed pomodoros, total focus time, estimated tasks done, focus score and the current phase.
The technique is named after the tomato-shaped (pomodoro, in Italian) kitchen timer that Francesco Cirillo used as a university student in the late 1980s when he devised the method.
It is a time-management method that breaks work into fixed focus intervals separated by short rests. The classic pattern is a 25-minute focus session followed by a 5-minute break, with a longer 15-minute break after every fourth pomodoro. This simulation lets you watch those cycles run and see their modelled effect on attention.
Each simulated minute the focus value starts at 0.75, adds a sinusoidal ultradian boost of up to 0.15 that peaks roughly every 90 minutes, subtracts a fatigue term that grows with time, and adds up to 0.3 from completed pomodoros. The result is clamped to a minimum of 0.1 and displayed as a percentage.
They set the focus and break durations. Pomodoro 25/5 uses 25-minute focus blocks with 5-minute breaks, Deep 90/20 uses 90-minute blocks with 20-minute breaks, and Sprint 15/3 uses 15-minute blocks with 3-minute breaks. Each mode also defines how often a longer break occurs and resets the counters when selected.
No — it is an illustrative model, not a clinical measurement. Real cortisol follows a complex daily rhythm and varies between people. Here cortisol simply rises across a focus phase and falls during breaks, while energy declines with fatigue, so the curves convey the idea of stress and recovery rather than precise physiological values.
The model embeds an ultradian rhythm — a natural cycle of about 90 to 120 minutes in human alertness. The sine term peaks once per 90-minute cycle, so attention crests and dips even as the slower daily fatigue pulls the baseline gradually downward. Structured breaks are meant to align rest with these natural troughs.