You're not lazy.
You're on the wrong clock.
ARC explains why you feel tired right now, gives you the one thing worth doing about it, and shows you over the weeks, from your own check-ins, whether it's working.
“Adenosine pressure peak. A 15-minute brisk walk or NSDR resets mental clarity.”
Clear Adenosine Backlog
Switch to hydration or a 10m walk
TRY IT · 20 SECONDS
When is your
last safe coffee?
It depends on three things: when you go to bed, how big the cup is, and how fast your body clears caffeine. The target is under 50 mg still in your system at bedtime.
2. Your usual cup
3. How fast you clear caffeine
Somewhere in between, or not sure. (5.5h half-life)
Your last safe coffee
12:00 PM
11h before your 11:00 PM bedtime.
A coffee-shop medium at 3:00 PM leaves 73 mg in you at bedtime.
Over the lineThis assumes it's your first caffeine today. ARC counts every drink you log and moves your cutoff each time. Free setup, then a 7-day free trial on the annual plan.
Tired in a way
sleep doesn't fix?
You've been told you're undisciplined because you can't function at 8:00 AM, or you're wired at midnight. It's not a character flaw — it's your chronotype. Your body runs on a biological clock, and most of us are fighting ours all day.
Mornings feel like fog until 10am
Your cortisol rise is delayed, keeping you in sleep mode long after your alarm.
The 3pm crash every single day
Drinking coffee at the wrong time blockades adenosine receptors, ensuring an afternoon crash.
Wide awake exactly when you need to sleep
Fluorescent lights and digital screens suppress melatonin, pushing your sleep gate back hours.
THE 4 CHRONOTYPES
There are four clocks.
Which is yours?
Your chronotype dictates when you're wired to wake, peak, and sleep. A 22-step onboarding across 6 acts pinpoints yours.
Lion
Early RiserEarly riser, peaks before noon, fades by evening.
Read full guide →Bear
Solar RhythmFollows the sun; 50% of the world runs on Bear time.
Read full guide →Wolf
Night OwlSlow mornings, sharp late — built for the night.
Read full guide →Dolphin
Light SleeperLight, sensitive sleeper with a busy mind.
Read full guide →
It explains today,
and proves it over weeks.
One sentence about why you feel the way you do, one thing worth doing about it, and over time, your own numbers showing whether it worked.
- 7:40 AM
One sentence, one thing to do
ARC opens with a sentence about where you are in your day and a single action. In the morning that's usually light: a 20-minute timer that runs on your lock screen and in the Dynamic Island, so your phone can stay in your pocket.
Sunrise comes from your time zone. No location permission, with an indoor fallback on dark winter mornings.
- 10:45 AM
Every coffee moves your cutoff
Log a drink in one tap and your last safe coffee recalculates from your bedtime, how fast you clear caffeine, and everything you've had today. Here, one espresso pulls it 4h earlier.
When no cup fits before bed anymore, ARC says so instead of showing a time.
- 2:40 PM
When the crash comes, so does the reason
At the dip, ARC tells you what's happening and asks for a walk, not another coffee. The why is one tap away, and the rest of your day sits underneath: what's done, and what's still open.
Then, over the next weeks
- Day 10
It stops taking your word for it
Once enough check-ins land, ARC measures when your dip really hits. If it's outside the window you picked on day one, it tells you, and everything timed around your dip moves with it.
- Day 28
Then it shows you what changed
Once a month, ARC puts your crash rate side by side, then versus now, from your own check-ins. Five-day experiments test one habit at a time, and “no difference” is an allowed answer.
No sleep score, no streaks, no rings.
HOW IT WORKS
Set up once,
then just live your day.
Your log lives on your iPhone, not on a server, and there's no score or streak to keep up.
Download ARC
Free on the App Store. There's no account to create and nothing to wear.
Tell it about your day
Your wake time, bedtime, when you usually crash, and how you take your coffee. You'll see your chronotype and a preview of your first day before you pay anything.
Tap in when you crash
One-tap check-ins are all it asks. They're how ARC learns when your dip really lands, and how it measures whether anything changed.
THE SCIENCE
Built on chronobiology,
not hustle culture.
Your energy isn't random — it follows a circadian rhythm set by light, sleep, and timing. ARC turns decades of sleep and circadian science into simple, personalized actions.
- Sleep Pressure
Adenosine
Sleep pressure, not laziness
Adenosine builds up in your brain from the moment you wake, and that sleep pressure is what the afternoon dip feels like. Caffeine doesn't remove it; it masks the signal until it wears off. ARC tracks how much caffeine is still on board and solves your last safe coffee from your bedtime.
- Morning Anchor
Cortisol
Morning light sets the clock
Cortisol rises naturally after waking, and morning daylight is the strongest signal for setting the body clock that times it, along with when you'll feel alert and when melatonin rises that evening. ARC works out your real sunrise and runs a 20-minute light timer.
- Sleep Onset
Melatonin
Wind-down, on your schedule
Melatonin rises in the evening on a schedule set by your body clock, and bright light late at night pushes it back. ARC's wind-down reminder tells you when to dim screens and lights, timed to your own bedtime.
Research Foundation
Dr. Andrew Huberman
Stanford Neuroscience Lab
Light exposure, cortisol rhythms & adenosine management
Dr. Matthew Walker
UC Berkeley Center for Sleep Science
Sleep architecture, circadian cycles & melatonin optimization
Finally understand
how your body works.
“Nice to know how my body works — the optimal time to drink coffee and when to cut it off so it doesn't affect my sleep.”
Sound Familiar?
Built for people who are
done guessing.
High-Performers
Founders, engineers, and creators who need maximum focus hours. ARC maps your peak windows so you stop guessing.
View Guide →Coffee Drinkers
You drink coffee every day but have never understood how it actually interacts with your sleep. ARC shows you the exact cutoff minute.
View Guide →ADHD Professionals
One sentence and one thing to do at a time, instead of an overwhelming list. A wellness app, not a treatment.
View Guide →Sleep Seekers
Sleeping 7-8 hours but still exhausted? It's a timing problem, not a duration problem. ARC fixes the root cause.
View Guide →Biohackers
Real data and correlations — not just streaks and checkboxes. Understand the cortisol-melatonin rhythm driving your entire day.
View Guide →Shift Workers
Design your flexible schedule around biology, not just calendar availability. Anchor your rhythm regardless of when you wake up.
View Guide →
PRICING
Start syncing
today.
Setup is free and shows your chronotype and first day. Then choose a plan: annual starts with a 7-day free trial. Useful from day one, and more personal after about 10 days of one-tap check-ins. Cancel anytime in the App Store.
Weekly
$4.99/ weekGet WeeklyCancel anytime in App Store
Annual
Save 84%Start 7-Day Free Trial7-day free trial, then
$39.99/ year~$0.77 / week after the trial • Billed annually
Have questions or a tight budget?
Whether you want to understand the science better, or you're a student experiencing financial hardship, we don't want price to be a barrier to your health.
Payment charged to Apple ID at purchase confirmation. Subscription auto-renews unless canceled 24h before end of period. Manage in App Store account settings.
FAQ
Questions
answered.
Why doesn't ARC have sleep scores (0-100), rings, or streaks?
A number out of 100 invites gaming an arbitrary score rather than understanding your body. Breaking a streak causes app abandonment. ARC rejects gamification and focuses on physiological mechanisms ('This is adenosine, not laziness') and measured proof: your afternoon crashes per week, from your own check-ins.
How does the dynamic caffeine cutoff work?
Unlike generic 'no coffee 8 hours before bed' rules, ARC computes your cutoff dynamically from your target bedtime, personal metabolic sensitivity (fast, normal, or slow), and every drink logged today to ensure under 50mg of active circulating caffeine remains at bedtime.
Do I need a wearable or Apple Watch?
No. ARC works completely standalone from your wake time, light timers, and quick one-tap check-ins. It calculates your biological rhythm without requiring expensive hardware.
Does ARC require GPS location permissions for morning light?
No location permission is ever requested. ARC calculates the true astronomical sunrise and solar angles directly from your device's time zone.
What is the 5-day experiment loop?
ARC tests one habit change at a time (like an earlier cutoff or pre-dip walk) for five days against your recorded history, scoring the outcome with honest verdicts including 'no difference'.
Is my data private?
Yes. ARC is built on local-first SQLite on your iPhone. There are no accounts, no logins, and no remote cloud database holding your check-ins or habits.
Does it work for shift workers?
Yes, for steady schedules. ARC plans around the wake and bed times you set and solves your caffeine cutoff from your real bedtime, even when it falls in the morning. Rotations that change every few days are harder to plan for.
How do I cancel?
Anytime in one tap through your Apple ID subscription settings.
START TODAY
Stop fighting
your clock.
Find your chronotype and build a day that works with your biology.
Download on theApp StoreFree setup, then a 7-day free trial (annual) or $4.99/week · Useful from day one, personal after about 10 days