/* Core UI shared by every brand: base, components, sign-in and mailbox.
   Reads only tokens from brands/<site-id>/theme.css. Brand page layout belongs to @layer site.
   Logical properties only (inline/block), so RTL locales need no second stylesheet. */
@layer reset, tokens, core, site;

@layer reset {
  *, *::before, *::after { box-sizing: border-box; }
  html { -webkit-text-size-adjust: 100%; text-size-adjust: 100%; }
  body { margin: 0; }
  :where(h1, h2, h3, h4, p, figure, blockquote, dl, dd) { margin: 0; }
  :where(ul, ol)[role="list"], :where(nav, .nav-group) :where(ul, ol) { margin: 0; padding: 0; list-style: none; }
  img, svg { display: block; max-inline-size: 100%; }
  button, input, select, textarea { font: inherit; color: inherit; }
  [hidden] { display: none !important; }
  @media (prefers-reduced-motion: reduce) {
    *, *::before, *::after { transition-duration: 0s !important; animation-duration: 0s !important; }
  }
}

@layer core {
  /* Label colors are user data, so the palette belongs to core, not to a brand. */
  :root {
    --label-blue: light-dark(oklch(52% 0.13 255), oklch(76% 0.1 255));
    --label-rose: light-dark(oklch(52% 0.15 0), oklch(76% 0.11 0));
    --label-teal: light-dark(oklch(52% 0.08 200), oklch(78% 0.08 200));
    --label-sand: light-dark(oklch(55% 0.09 75), oklch(80% 0.09 75));
  }
  @media (prefers-contrast: more) {
    :root { --color-rule: var(--color-rule-strong); --color-ink-3: var(--color-ink-2); }
  }

  body {
    font-family: var(--font-ui);
    font-size: 1rem;
    line-height: 1.5;
    color: var(--color-ink);
    background: var(--color-paper);
    -webkit-font-smoothing: antialiased;
  }
  html.i18n-pending body { opacity: 0; }
  ::selection { background: var(--color-rubric-tint); color: var(--color-ink); }
  a {
    color: inherit;
    text-decoration-thickness: 1px;
    text-underline-offset: 0.2em;
    text-decoration-color: var(--color-rule-strong);
  }
  a:hover { text-decoration-color: var(--color-rubric); }
  :focus-visible { outline: 2px solid var(--color-focus); outline-offset: 2px; }
  code { font-family: var(--font-mono); font-size: 0.92em; }
  /* A missing translation shows its key instead of silently disappearing. */
  [data-i18n]:empty::before { content: attr(data-i18n); color: var(--color-danger); font: 0.75rem var(--font-mono); }

  .visually-hidden {
    position: absolute; inline-size: 1px; block-size: 1px; margin: -1px; padding: 0;
    overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0;
  }

  .icon {
    inline-size: 1.125rem; block-size: 1.125rem; flex: none;
    fill: none; stroke: currentColor; stroke-width: 1.5; stroke-linecap: round; stroke-linejoin: round;
  }
  [dir="rtl"] .icon--flip { scale: -1 1; }

  .brand {
    display: inline-flex; align-items: center; gap: 0.625rem;
    color: var(--color-ink); text-decoration: none;
    font: 400 1.3125rem/1 var(--font-display); letter-spacing: -0.005em;
  }
  .brand img { inline-size: 1.75rem; block-size: 1.75rem; }

  /* Buttons. Primary actions are set in ink; the rubric is never a button fill. */
  .btn {
    display: inline-flex; align-items: center; justify-content: center; gap: 0.5em;
    min-block-size: 2.5rem; padding-inline: 1rem;
    border: 1px solid transparent; border-radius: var(--radius-s);
    font: 700 0.9375rem/1.2 var(--font-ui); text-align: center; text-decoration: none;
    cursor: pointer; transition: background-color 0.15s, border-color 0.15s, color 0.15s;
  }
  .btn--primary { background: var(--color-ink); color: var(--color-on-ink); }
  .btn--primary:hover { background: color-mix(in oklch, var(--color-ink) 84%, var(--color-rubric)); color: var(--color-on-ink); }
  .btn--secondary { border-color: var(--color-rule-strong); background: transparent; color: var(--color-ink); }
  .btn--secondary:hover { border-color: var(--color-ink); }
  .btn--quiet { background: transparent; color: var(--color-ink-2); }
  .btn--quiet:hover { background: var(--color-paper-2); color: var(--color-ink); }
  .btn--sm { min-block-size: 2rem; padding-inline: 0.75rem; font-size: 0.875rem; }
  .btn--lg { min-block-size: 3rem; padding-inline: 1.5rem; font-size: 1rem; }
  .btn--block { inline-size: 100%; }
  .btn:disabled { cursor: not-allowed; opacity: 0.55; }
  .btn[aria-busy="true"] { cursor: progress; opacity: 0.75; }

  .icon-btn {
    display: inline-grid; place-items: center; inline-size: 2.25rem; block-size: 2.25rem;
    border: 0; border-radius: var(--radius-s); background: transparent; color: var(--color-ink-2); cursor: pointer;
  }
  .icon-btn:hover { background: var(--color-paper-2); color: var(--color-ink); }

  /* Delivery marks, like a postmark: same words and glyphs on every brand. */
  .badge {
    display: inline-flex; align-items: center; gap: 0.375rem; padding: 0.125rem 0.5rem;
    border: 1px solid currentColor; border-radius: var(--radius-s);
    font: 700 0.8125rem/1.4 var(--font-ui);
  }
  .badge .icon { inline-size: 1rem; block-size: 1rem; }
  .badge--sealed { background: var(--color-sealed-tint); color: var(--color-sealed); }
  .badge--postcard { background: var(--color-postcard-tint); color: var(--color-postcard); }
  .badge--neutral { border-color: var(--color-rule-strong); color: var(--color-ink-2); }

  /* Language switcher: Popover API, language names in their own language. */
  .locale [popover] {
    position: fixed; inset: auto; inset-block-start: 3.75rem; inset-inline-end: 1rem; margin: 0;
    min-inline-size: 12rem; padding: 0.375rem;
    border: 1px solid var(--color-rule-strong); border-radius: var(--radius-m);
    background: var(--color-field); color: var(--color-ink);
    box-shadow: 0 1rem 2rem -1rem oklch(0% 0 0 / 0.35);
  }
  .locale [popover] a {
    display: block; padding: 0.5rem 0.75rem; border-inline-start: 2px solid transparent;
    color: var(--color-ink); text-decoration: none;
  }
  .locale [popover] a:hover { background: var(--color-paper-2); }
  .locale [popover] a[aria-current] { border-inline-start-color: var(--color-rubric); font-weight: 700; }

  /* Forms */
  .field { display: grid; gap: 0.375rem; }
  .label { font-size: 0.9375rem; font-weight: 700; }
  .hint { font-size: 0.875rem; color: var(--color-ink-2); }
  .control {
    display: flex; align-items: stretch; min-block-size: 2.875rem;
    border: 1px solid var(--color-rule-strong); border-radius: var(--radius-s); background: var(--color-field);
  }
  .control:focus-within { border-color: var(--color-ink); outline: 2px solid var(--color-focus); outline-offset: 1px; }
  .control[data-invalid="true"] { border-color: var(--color-danger); }
  .control input { flex: 1 1 0; min-inline-size: 0; padding-inline: 0.75rem; border: 0; background: transparent; outline: none; }
  .control input::placeholder { color: var(--color-ink-3); }
  .control .icon-btn { align-self: center; margin-inline-end: 0.25rem; }
  .control__at { display: grid; place-items: center; padding-inline: 0.125rem; color: var(--color-ink-3); font-family: var(--font-mono); }
  .control__select { position: relative; display: flex; flex: none; max-inline-size: 62%; border-inline-start: 1px solid var(--color-rule); }
  .control__select select {
    inline-size: 100%; min-inline-size: 0; padding-inline: 0.625rem 2rem;
    border: 0; background: var(--color-paper-2); appearance: none; outline: none;
    font: 0.875rem var(--font-mono);
  }
  .control__select .icon {
    position: absolute; inset-inline-end: 0.5rem; inset-block-start: 50%; translate: 0 -50%;
    inline-size: 1rem; block-size: 1rem; color: var(--color-ink-2); pointer-events: none;
  }
  .form-error {
    display: flex; align-items: flex-start; gap: 0.625rem; padding: 0.625rem 0.75rem;
    border-inline-start: 3px solid var(--color-danger); background: var(--color-danger-tint);
    color: var(--color-danger); font-size: 0.9375rem;
  }
  .form-error .icon { margin-block-start: 0.125rem; }

  /* Sign-in defaults: a sheet with a margin note. A brand restyles these classes in its own layer
     (parent16: brands/parent16/auth.css), the markup and behaviour stay core. */
  .auth__main { container-type: inline-size; padding: clamp(2rem, 9vh, 6rem) clamp(1rem, 4vw, 2.5rem); }
  .auth__sheet { display: grid; grid-template-columns: minmax(0, 26rem); gap: 2.5rem; justify-content: center; align-content: start; }
  @container (inline-size > 52rem) {
    .auth__sheet { grid-template-columns: minmax(0, 26rem) minmax(0, 15rem); column-gap: 4.5rem; }
    .margin-note { margin-block-start: 6.25rem; }
  }
  .auth__title { margin-block-end: 0.5rem; font: 400 clamp(2rem, 1.6rem + 1.6vw, 2.75rem)/1.1 var(--font-display); letter-spacing: -0.012em; }
  .auth__lead { margin-block-end: 2rem; color: var(--color-ink-2); }
  .auth__form { display: grid; gap: 1.25rem; }
  .auth__links { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 0.5rem 1rem; margin-block-start: 1.5rem; font-size: 0.9375rem; }
  .margin-note {
    display: grid; gap: 0.75rem; align-content: start; padding-block-start: 0.75rem;
    border-block-start: 2px solid var(--color-ink); color: var(--color-ink-2); font-size: 0.875rem;
  }
  .margin-note .icon { color: var(--color-ink-2); }

  /* Account (TASK-054): passkey sign-in, registration, recovery. One [data-panel] is visible at a time;
     every panel keeps the main column in the same place, so switching modes does not move the form. */
  .sprite { position: absolute; inline-size: 0; block-size: 0; overflow: hidden; }
  /* Headings take focus only so a screen reader announces the new panel; they are not controls. */
  .auth__title:focus { outline: none; }
  .auth__title + .auth__form { margin-block-start: 1.5rem; }
  .auth__status:empty, .auth__lead[data-status]:empty { display: none; }
  .auth__status { color: var(--color-ink-2); font-size: 0.9375rem; }
  .auth__subtitle { font: 400 1.375rem/1.25 var(--font-display); letter-spacing: -0.005em; }
  /* Only fields the page marked: inputs it empties after a failed attempt must not look wrong by themselves. */
  .control:has(input[aria-invalid="true"]) { border-color: var(--color-danger); }
  .control--code input { font-family: var(--font-mono); letter-spacing: 0.02em; }
  /* A reserved place for a human check (CAPTCHA): widgets are about 78px tall, so the form does not jump when one appears. */
  .captcha:not([hidden]) { display: grid; justify-items: center; min-block-size: 4.875rem; }
  [data-copy-missing]::before { content: attr(data-copy); color: var(--color-danger); font: 0.75rem var(--font-mono); }

  .account-id { margin-block: 0.25rem 1.25rem; font: 1.125rem/1.4 var(--font-mono); overflow-wrap: anywhere; }
  .auth__part, .auth__actions { margin-block-start: 2rem; padding-block-start: 1.25rem; border-block-start: 1px solid var(--color-rule); }
  .auth__part { display: grid; gap: 0.75rem; justify-items: start; }
  .auth__part > .form-error, .auth__part > .hint { justify-self: stretch; }
  .auth__actions { display: flex; flex-wrap: wrap; gap: 0.5rem; }
  .auth__actions > .form-error { flex-basis: 100%; }
  .state { display: flex; align-items: flex-start; gap: 0.5rem; }
  .state .icon { margin-block-start: 0.1875rem; color: var(--color-ink-2); }
  .state[data-state="ready"] .state__missing, .state[data-state="missing"] .state__ready { display: none; }

  /* A tear-off slip: the code is shown once, so it is set apart like a counterfoil to keep. */
  .slip {
    display: grid; gap: 0.875rem; justify-self: stretch; justify-items: start; padding: 1.25rem;
    border: 1px dashed var(--color-rule-strong); border-radius: var(--radius-s); background: var(--color-field);
  }
  .slip__warn { display: flex; align-items: flex-start; gap: 0.5rem; font-weight: 700; }
  .slip__warn .icon { margin-block-start: 0.1875rem; }
  .slip__warn:focus { outline: none; }
  .slip__code {
    display: block; justify-self: stretch; padding: 0.75rem 0.875rem; background: var(--color-paper-2);
    font: 1.125rem/1.5 var(--font-mono); letter-spacing: 0.02em; overflow-wrap: anywhere; user-select: all;
  }
  .slip__note { color: var(--color-ink-2); font-size: 0.875rem; }

  /* Mailbox */
  .app {
    block-size: 100vh; block-size: 100dvh;
    display: grid;
    grid-template-columns: 15rem minmax(20rem, 26rem) minmax(0, 1fr);
    grid-template-rows: 3.5rem minmax(0, 1fr);
    grid-template-areas: "top top top" "nav list reader";
  }
  .app__top {
    grid-area: top; display: flex; align-items: center; gap: 1rem; padding-inline: 1rem;
    background: var(--color-paper); border-block-end: 1px solid var(--color-rule);
  }
  .app__top .brand { inline-size: 13rem; flex: none; font-size: 1.1875rem; }
  .app__menu { display: none; }
  .search {
    display: flex; align-items: center; gap: 0.5rem; flex: 1; min-inline-size: 0; max-inline-size: 36rem; block-size: 2.375rem; padding-inline: 0.75rem;
    border: 1px solid var(--color-rule); border-radius: var(--radius-s); background: var(--color-field); color: var(--color-ink-3);
  }
  .search:focus-within { border-color: var(--color-ink); outline: 2px solid var(--color-focus); outline-offset: 1px; }
  .search input { flex: 1; min-inline-size: 0; border: 0; background: transparent; outline: none; color: var(--color-ink); }
  .search input::placeholder { color: var(--color-ink-3); }
  .account { display: flex; align-items: center; gap: 0.625rem; margin-inline-start: auto; }
  .account__addr { font: 0.8125rem var(--font-mono); color: var(--color-ink-2); }
  .avatar {
    display: grid; place-items: center; inline-size: 2rem; block-size: 2rem; flex: none; border-radius: 50%;
    border: 1px solid var(--color-rule-strong); background: var(--color-paper-2); font: 700 0.75rem var(--font-ui);
  }

  .app__nav { grid-area: nav; overflow: auto; padding: 1rem 0.75rem; background: var(--color-paper-2); border-inline-end: 1px solid var(--color-rule); }
  .compose-btn { inline-size: 100%; margin-block-end: 1.25rem; }
  .nav-group { margin-block-end: 1.5rem; }
  .nav-group__title { padding-inline: 0.625rem; margin-block-end: 0.25rem; color: var(--color-ink-3); font-size: 0.8125rem; font-weight: 700; }
  .nav-item {
    position: relative; display: flex; align-items: center; gap: 0.625rem;
    min-block-size: calc(2.125rem * var(--density)); padding-inline: 0.625rem;
    border-radius: var(--radius-s); color: var(--color-ink-2); font-size: 0.9375rem; text-decoration: none;
  }
  .nav-item:hover { background: var(--color-paper); color: var(--color-ink); }
  .nav-item[aria-current="page"] { background: var(--color-paper); color: var(--color-ink); font-weight: 700; }
  .nav-item[aria-current="page"]::before {
    content: ""; position: absolute; inset-block: 0.375rem; inset-inline-start: -0.75rem; inline-size: 3px; background: var(--color-rubric);
  }
  .nav-item__count { margin-inline-start: auto; color: var(--color-ink-2); font-size: 0.8125rem; font-variant-numeric: tabular-nums; }
  .dot { inline-size: 0.625rem; block-size: 0.625rem; margin-inline: 0.25rem; flex: none; border-radius: 2px; background: var(--dot); }
  .dot--blue { --dot: var(--label-blue); }
  .dot--rose { --dot: var(--label-rose); }
  .dot--teal { --dot: var(--label-teal); }
  .dot--sand { --dot: var(--label-sand); }

  .app__list { grid-area: list; overflow: auto; background: var(--color-paper); border-inline-end: 1px solid var(--color-rule); }
  .list-head {
    position: sticky; inset-block-start: 0; z-index: 1;
    display: flex; flex-wrap: wrap; align-items: baseline; justify-content: space-between; gap: 0.25rem 0.75rem;
    padding: 1rem 1rem 0.75rem; background: var(--color-paper); border-block-end: 1px solid var(--color-ink);
  }
  .list-head h1 { font: 400 1.5rem/1.2 var(--font-display); }
  .list-head__meta { color: var(--color-ink-2); font-size: 0.8125rem; }
  .msg {
    position: relative; display: grid; grid-template-columns: auto minmax(0, 1fr) auto; gap: 0.125rem 0.625rem;
    padding: calc(0.75rem * var(--density)) 1rem calc(0.75rem * var(--density)) 1.25rem;
    border-block-end: 1px solid var(--color-rule); color: inherit; text-decoration: none;
  }
  .msg:hover { background: var(--color-paper-2); }
  .msg[aria-current="true"] { background: var(--color-paper-2); }
  .msg[aria-current="true"]::before { content: ""; position: absolute; inset-block: 0; inset-inline-start: 0; inline-size: 3px; background: var(--color-rubric); }
  .msg--unread::after {
    content: ""; position: absolute; inset-inline-start: 0.5rem; inset-block-start: calc(1.25rem * var(--density));
    inline-size: 0.375rem; block-size: 0.375rem; border-radius: 50%; background: var(--color-rubric);
  }
  .msg__glyph { inline-size: 1rem; block-size: 1rem; margin-block-start: 0.1875rem; }
  .msg__glyph--sealed { color: var(--color-sealed); }
  .msg__glyph--postcard { color: var(--color-postcard); }
  .msg__from, .msg__subject, .msg__snippet { min-inline-size: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .msg__from { font-size: 0.9375rem; }
  .msg__time { color: var(--color-ink-2); font-size: 0.8125rem; font-variant-numeric: tabular-nums; white-space: nowrap; }
  .msg__subject, .msg__snippet, .msg__meta { grid-column: 2 / -1; }
  .msg__subject { font-size: 0.9375rem; }
  .msg__snippet { color: var(--color-ink-2); font-size: 0.875rem; }
  .msg--unread .msg__from, .msg--unread .msg__subject { font-weight: 700; }
  .msg__meta { display: flex; flex-wrap: wrap; align-items: center; gap: 0.375rem 0.75rem; margin-block-start: 0.25rem; }
  .msg__meta > .icon { inline-size: 0.875rem; block-size: 0.875rem; color: var(--color-ink-3); }
  .tag { display: inline-flex; align-items: center; gap: 0.3rem; color: var(--color-ink-2); font-size: 0.75rem; }
  .tag .dot { inline-size: 0.4375rem; block-size: 0.4375rem; margin: 0; }

  .app__reader { grid-area: reader; overflow: auto; background: var(--color-paper); container-type: inline-size; }
  .reader { max-inline-size: 46rem; margin-inline: auto; padding: 1rem 2rem 4rem; }
  .reader__toolbar { display: flex; align-items: center; gap: 0.125rem; margin-inline: -0.5rem; margin-block-end: 1.25rem; }
  .reader__toolbar .sep { inline-size: 1px; block-size: 1.25rem; margin-inline: 0.375rem; background: var(--color-rule); }
  .reader__back { display: none; }
  .reader__subject { margin-block-end: 1.25rem; font: 400 clamp(1.5rem, 1.1rem + 2cqi, 2.125rem)/1.2 var(--font-display); letter-spacing: -0.01em; }
  .reader__head {
    display: grid; grid-template-columns: auto minmax(0, 1fr) auto; gap: 0.75rem; align-items: start;
    padding-block-end: 1rem; border-block-end: 1px solid var(--color-rule);
  }
  .reader__name { font-weight: 700; }
  .reader__addr, .reader__to, .reader__date { color: var(--color-ink-2); font-size: 0.8125rem; }
  .reader__addr { font-family: var(--font-mono); }
  .reader__date { white-space: nowrap; }
  .reader__states { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-block: 1rem; }
  .notice {
    display: flex; flex-wrap: wrap; align-items: center; gap: 0.625rem 0.75rem; margin-block-end: 1rem; padding: 0.625rem 0.75rem;
    border: 1px solid var(--color-rule); border-inline-start: 3px solid var(--color-ink-3);
    background: var(--color-paper-2); color: var(--color-ink-2); font-size: 0.875rem;
  }
  .notice > span { flex: 1 1 14rem; }
  .notice .btn { margin-inline-start: auto; }
  .letter {
    padding: 1.75rem 2rem; border: 1px solid var(--color-rule); background: var(--color-field);
    font: 1.0625rem/1.65 var(--font-text); hyphens: auto;
  }
  .letter p + p, .letter p + .blocked-image, .letter .blocked-image + p { margin-block-start: 1em; }
  .blocked-image {
    display: flex; align-items: center; justify-content: center; gap: 0.5rem; block-size: 8rem;
    border: 1px dashed var(--color-rule-strong); background: var(--color-paper-2);
    color: var(--color-ink-3); font: 0.8125rem var(--font-ui);
  }
  .attachments { display: flex; flex-wrap: wrap; gap: 0.625rem; margin-block-start: 1rem; }
  .attachment {
    display: flex; align-items: center; gap: 0.625rem; padding: 0.625rem 0.875rem;
    border: 1px solid var(--color-rule-strong); border-radius: var(--radius-s); background: var(--color-field);
    font-size: 0.875rem; text-decoration: none;
  }
  .attachment > .icon { color: var(--color-ink-2); }
  .attachment small { display: block; color: var(--color-ink-2); font-size: 0.75rem; }
  .reply-bar {
    display: flex; flex-wrap: wrap; align-items: center; gap: 0.5rem; margin-block-start: 1.5rem; padding-block-start: 1rem;
    border-block-start: 2px solid var(--color-ink);
  }
  .reply-bar .badge { margin-inline-start: auto; }
  @container (inline-size < 32rem) {
    .reader__head { grid-template-columns: auto minmax(0, 1fr); }
    .reader__date { grid-column: 2; }
    .letter { padding: 1.25rem; }
    .reply-bar .badge { margin-inline-start: 0; }
  }

  @media (width < 70rem) {
    .app { grid-template-columns: minmax(18rem, 24rem) minmax(0, 1fr); grid-template-areas: "top top" "list reader"; }
    .app__top .brand { inline-size: auto; }
    .app__menu { display: inline-grid; }
    .app__nav {
      position: fixed; inset-block: 3.5rem 0; inset-inline-start: 0; z-index: 5; inline-size: 17rem;
      box-shadow: 0 1rem 2rem -1rem oklch(0% 0 0 / 0.35);
      translate: -100% 0; visibility: hidden; transition: translate 0.2s ease, visibility 0.2s;
    }
    [dir="rtl"] .app__nav { translate: 100% 0; }
    .app--nav-open .app__nav { translate: 0 0; visibility: visible; }
    .account__addr { display: none; }
  }
  @media (width < 45rem) {
    .app { grid-template-columns: minmax(0, 1fr); grid-template-areas: "top" "list"; }
    .app__top { gap: 0.5rem; padding-inline: 0.25rem 0.5rem; }
    .app__top .brand span, .app__top [data-locale-current] { display: none; }
    .app__reader { display: none; }
    .app--reading .app__list { display: none; }
    .app--reading .app__reader { display: block; grid-area: list; }
    .reader { padding-inline: 1rem; }
    .reader__back { display: inline-grid; }
  }

  @media (forced-colors: active) {
    .btn--primary, .control, .search { border-color: ButtonText; }
    .nav-item[aria-current="page"]::before, .msg[aria-current="true"]::before, .msg--unread::after { background: Highlight; }
  }
}