Focus
Short Break
Long Break
25:00
A free 90-minute timer for deep, uninterrupted work. Ninety minutes is roughly one full swing of the body's natural cycle of focus and energy, long enough to get fully absorbed in something hard before you need a real break. It is the block for your most demanding work, and a guide to shape to your own rhythm, not a rule.
Long, protected blocks are where genuinely hard work happens. Ninety minutes gives you room to load a whole problem into your head and actually solve it, instead of stopping just as it clicks.
A long runway: ninety minutes is enough to get past the warm-up and into a real flow of drafting before fatigue sets in.
Reading closely, following a thread, or untangling something complex all reward sustained attention. Give them one long block, not a string of short ones.
Hold the whole picture in view and explore, discard, and refine in one continuous pass.
A thorny bug, a tricky proof, a tangled dataset: hard problems reward one long, unbroken block where you can keep the whole thing in mind.
Your alertness and energy do not hold steady through the day; they rise and fall in cycles. Nathaniel Kleitman called this the basic rest-activity cycle, a roughly 90-minute rhythm he argued runs through waking life as well as sleep[1]. Performance follows it: when researchers tested people every fifteen minutes for hours, different kinds of thinking rose and fell on a 90-to-100-minute cycle[1]. A 90-minute block aims to give you one full swing of that cycle, a long stretch of deep focus before a natural dip, which is what makes it suit your most absorbing work.
Ninety minutes is also long enough to do what shorter blocks cannot: load an entire complex problem into your head and hold it there long enough to actually solve it, rather than stopping just as it starts to come together. The trade-off is that focus this sustained is tiring, so a block this long only pays off if you protect it from interruptions and follow it with a genuine break, not just another screen.
This is the honest part, and it is the heart of how we think about timers. That 90 minutes is an average, not a fixed clock. The cycle's length shifts between morning and afternoon and even drifts within a single day[1], and it differs from person to person. So treat 90 as a rhythm to work with: if you are still flowing at the bell, finish your thought; if you fade at seventy minutes, stop at seventy. The timer is here to help you find your own cycle, not to override it.