Cistern

Cistern is a quiet water intake tracker drawn in the visual language of the Basilica Cistern of Istanbul — a vaulted underground chamber where rows of columns rise from still teal water and warm amber lamplight pools across the surface. The home screen is the cistern itself, seen in cross-section: arches span the top, three columns descend into the chamber, and as you drink through the day the teal water rises from the floor toward the vaults.

The home screen is arranged differently from the usual tracker. Directly under the wordmark sits an INLINE STATS STRIP — three columns reading STREAK, WEEK AVG and MEASURES, divided by thin stone rules, so the day's discipline is the first thing you see. Below it is the CISTERN HERO: the vaulted cross-section described above, with the running total floating in a calm serif numeral in the dry upper chamber ("1.24 L of 2.00 L"), a small percent chip beneath it, and amber lamp reflections riding the water surface. Below the hero is TODAY'S MEASURES — a vertical list of everything you have drawn so far, each row introduced by a small amber lamp dot and a brass rule, with the clock time, the amount, and the vessel name. When the day's goal is met, a quiet teal banner crosses below the hero: THE CISTERN IS FULL.

The biggest change is the QUICK-ADD DOCK. Instead of a grid or a scrolling row buried in the page, the four quick-add vessels live in a FIXED BOTTOM DOCK that never scrolls away — it stays anchored to the bottom of the screen the whole time, so a measure is always one tap away no matter how far down the log you have scrolled. Each vessel is drawn as a classical column: a brass capital, a fluted shaft that fills with water to show the vessel's relative size, and a brass base. Tap a column and that measure pours into the cistern; the water rises another notch.

Tapping the arch icon opens VAULTS — the historical view. A 14-day strip at the top shows each day as a tiny arch-topped chamber filling with teal water, brighter on full days. Below it is a 30-day list where every day is its own vault: a small arch that fills to that day's proportion of the goal, a FULL badge in teal when the day reached the vaults, the day's total in a calm serif numeral, and the count of measures.

The settings live in UNDERCROFT — the lowest chamber of the cistern. There you can:
- Adjust the daily fill target in 100 ml steps (1.0 L – 4.5 L; or fluid ounces if you prefer)
- Switch units between metric (ml / L) and US fluid ounces
- Re-size each of the four column vessels (Sip / Glass / Cup / Bottle)
- Toggle haptic feedback on button taps
- Toggle between Cistern Night and a parchment day palette

The app remembers up to a year of entries on the device. There is no account, no cloud, no sync — everything you pour lives only on your phone. Records older than a year are pruned to keep the database small. The vaults are yours to keep or to drain.

Cistern doesn't nag, doesn't send notifications, doesn't try to gamify hydration. It just gives you a quiet underground chamber to fill: water rising slowly between the columns, lamplight on the surface, a streak that grows by being kept, a row of past days with the full ones marked in teal.

Still water below.