NightCurve: Drink Tracker

Solo dev, full-time job. Built a mindful drinking tracker (NightCurve) after wedding-night math problems.

Okay, picture this.

It's 2am. You're at a friend's wedding. You've had four beers and maybe a shot. Tomorrow you have a 9am meeting. You're trying to do mental math: how drunk am I, how hungover will I be, should I set my alarm later?

The variables you need are not the ones reliably accessible at 2am: exact drink count, alcohol percent, when you started, your weight, meal timing. So you guess. Set the alarm at 7. Wake up wrecked. Tell yourself "never again." Repeat in three weeks.

I was the guy doing this math for years. Then one Friday I thought: this is the app I'd want to use. Tap drinks as I go, see where I stand right now, get a rough estimate of when I'll be functional again. Not promille. Not BAC. Just zones (Fresh, Light, Mild, Heavy, Overload) and recovery times.

So I built NightCurve.

What I shipped:

- iOS app, mindful drinking tracker

- Tap drinks → see zones → get recovery estimate

- Apple Watch ready, Live Activity support

- No shame framing, no recovery talk — just data for people who drink occasionally

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2 lessons from launching as a solo dev:

1. Apple iterations are product feedback in disguise.

NightCurve went through 3 review iterations. Each one pushed me toward better positioning — away from "BAC tracker" toward "wellness tool with zones." Same underlying math, different framing. In retrospect, Apple's bar was right. The app got cleaner because of it. Lesson: framing >> features.

2. The audience self-selects.

I built this for "the guy doing 2am math." Turns out that's a real demographic: damp lifestyle, sober curious, mindful drinking. Not "alcoholics" (recovery apps exist), not "party people" (they don't track). Middle ground: people who drink occasionally and want to plan tomorrow. Lesson: build for a specific moment, not a vague segment.

— Marcin

appsbymarcin.com