Privacy-Period-Tracker/docs/design/README.md

# Design

```
Status: Current
Owner: _null
Last reviewed: 2026-08-18
Governs: docs/design/**, the design tokens in core/designsystem, and the product's
         tone and interface copy
Review trigger: Any new user-facing screen or state; any change to the colour or
                type tokens; any change to notification copy or to a privacy or
                fertility disclaimer
```

## Where the detail is

The screen-by-screen specification and the actual words are
[`../planning/PRODUCT_PLAN.md`](../planning/PRODUCT_PLAN.md), and they are not
repeated here — a second copy of interface copy is how two versions of a
disclaimer come to exist.

| Subject | Section it owns |
| --- | --- |
| Onboarding, seven screens, with copy | §19, §56 |
| Navigation — four tabs | §20 |
| Today screen and its six dynamic states | §21, §22 |
| Period logging, period end, spotting | §23, §24, §25 |
| Calendar states and markers | §26 |
| Insights | §27 |
| Notification modes, types and flow | §28, §29, §30 |
| Incognito launcher | §32 |
| Look and feel, visual direction, colour, typography, motion | §37–§41 |
| Artwork | §42 |
| Accessibility | §43 |

This document holds what governs those: the tone, and the rules that decide an
argument the specification did not anticipate.

## Tone

Calm, private, intelligent, adult. The app is a good utility with warmth — it is
not clinical, not childish, not gamified, and not stereotypically feminine as an
identity. It never celebrates a period and never alarms about one.

One paragraph, and it settles most small arguments: **the app speaks like
someone competent who is not making a fuss.** "Your period is late!" is out.
"Not yet?" with an updated forecast is in.

## Four rules that decide the arguments

**1. The number is the hero.** The forecast dominates the Today screen —
[§38](../planning/PRODUCT_PLAN.md). Anything competing with it for attention is
wrong, including anything of ours.

**2. Nothing asserts certainty the model does not have.** A window and a
confidence label, never a bare exact date presented as fact. "Estimated
ovulation", never "you are ovulating today". Fertility copy carries the
not-contraception line wherever it appears.

**3. State is never colour alone.** Confirmed period is a solid fill, predicted
is dotted or outlined, fertile window is a ring, ovulation is its own small
marker — distinguishable in greyscale, because that is also what makes them
distinguishable to a colourblind user and to a screenshot in a bug report.
Predicted and confirmed days must never look identical.

**4. Ads never touch a health action.** No banner in onboarding, in the
period-start confirmation, in the period-end confirmation, or between steps of a
health workflow — and never an interstitial after logging
([§33](../planning/PRODUCT_PLAN.md)). Banner space is reserved in the layout so a
failed ad does not move the content.

## Colour, in one line each

The palette is [§39](../planning/PRODUCT_PLAN.md); the constraints on it are:

- **Not pink as the whole identity.** Deep plum, muted berry, soft lavender,
  warm cream, charcoal, muted sage/teal.
- **Period state** is a sophisticated berry or plum — never graphic blood-red.
- **Fertile window** is muted teal or sage — never bright green, which reads as
  *safe* and this app must never say that.
- Everything goes through Material 3 colour roles and centralized tokens in
  `core/designsystem`. **No hard-coded colours in a Composable** — the guard is
  that a colour literal outside the token file is a review failure.

## Both themes, every time

Dark mode was broken for the whole of Batch 01 and nothing said so. `PeriodTheme`
was not wrapping its content in a `Surface`, so any `Text` without an explicit
colour inherited Material's default — black — and the app's own background never
painted at all. **In light mode that looked correct by accident**, because dark
text on cream is what was wanted anyway; in dark mode the onboarding headings
were near-black on charcoal.

No test caught it and no test easily would. It was found by opening the app.

Two rules follow. Every screen gets a **preview pair, light and dark** — cheap,
and it puts the failure in front of whoever is editing. And the `Surface` lives
in the theme rather than in each screen, so a screen without a `Scaffold` cannot
forget it.

## The states most often left undesigned

Designed here on purpose, because they are the two most people meet first:

- **Empty** — no periods logged yet. It has to make the next action obvious
  rather than apologise.
- **Learning** — one or two cycles recorded. The app says it is still learning
  rather than showing a confident forecast it has not earned. "Getting to know
  your pattern", not a percentage.

## The artwork is placeholder, and says so here

Every illustration and calendar marker in the app is a **Compose vector path**
in [`core/designsystem/src/main/kotlin/dev/privacyllc/period/designsystem/art/`](../../core/designsystem/src/main/kotlin/dev/privacyllc/period/designsystem/art/), written as PRODUCT_PLAN.md §42 asks: polished
placeholders behind replaceable names, so real artwork changes one function body
and no call site.

The visual language is deliberately narrow — **overlapping circular forms** and
nothing else. §42's forbidden list (blood drops, tampons, pads, uterus imagery,
gender symbols, anatomy) is a product decision rather than squeamishness: this
app gets opened in public, and somebody glancing over a shoulder should learn
nothing. That is a property of the pictures as much as of the notification text.

**Note the deliberate inconsistency with `docs/data/img/`,** where a placeholder
is forbidden. The rule there is that an image which looks finished outlives the
issue that would have replaced it, because nobody files a ticket against
something that appears done. In-app assets escape that because §42 asks for them
explicitly and the replaceable-name mechanism is what keeps them replaceable —
and because a screen with no illustration cannot be evaluated at all, while a
project card with no icon simply shows initials.

## Include the rejected version

For any decision that was genuinely close, record what was not chosen and why.
Without it the same option is proposed again every few months and re-argued from
nothing. The first entries belong to whoever makes those calls; the
specification's `Avoid:` lists are already a partial record of them.

## What does not belong here

- How it is built — [`../architecture/README.md`](../architecture/README.md)
- Scope and audience — [`../planning/PROJECT_PLAN.md`](../planning/PROJECT_PLAN.md)