/* ============================================================
   MorseFlare — layout & design system (v4)
   Centered, balanced layout. No external dependencies.
   ============================================================ */
:root {
  --ink: #0B1F2A;
  --ink-2: #14313F;
  --paper: #F5F8F9;
  --surface: #FFFFFF;
  --body: #2A3B44;
  --muted: #5F7079;
  --line: #DDE6EA;
  --line-2: #C9D6DB;
  --signal: #0E8F78;
  --signal-2: #14C4A3;
  --signal-ink: #0A6B5A;
  --flare: #E8A317;
  --flare-ink: #7A4E04;
  --tint: #E9F7F3;
  --tint-2: #F1FAF7;
  --warn-bg: #FEF6E7;
  --warn-line: #F1D8A4;
  --radius: 16px;
  --shadow: 0 1px 2px rgba(11, 31, 42, .05), 0 12px 30px rgba(11, 31, 42, .06);
  --shadow-lg: 0 26px 60px rgba(11, 31, 42, .14);
  --maxw: 1120px;
  --font-sans: "IBM Plex Sans", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, "SFMono-Regular", Menlo, "Courier New", monospace;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; text-size-adjust: 100%; }

body {
  margin: 0;
  min-height: 100vh;
  background: var(--paper);
  color: var(--body);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4 { color: var(--ink); line-height: 1.18; letter-spacing: -.025em; margin: 0; font-weight: 650; }
a { color: var(--signal-ink); }
img, svg { max-width: 100%; } svg { height: auto; }
[hidden] { display: none !important; }
.mf-flash { display: none !important; }
.mf-flash.is-on { display: grid !important; }

:focus-visible { outline: 3px solid var(--signal-2); outline-offset: 2px; }
::selection { background: rgba(20, 196, 163, .28); }

/* ---------- shell ---------- */
.mf-app { min-height: 100vh; display: flex; flex-direction: column; }
.mf-main { flex: 1; padding-bottom: 4.5rem; }
.mf-wrap {
  width: min(var(--maxw), calc(100% - 2.5rem));
  margin-inline: auto;
}

/* ---------- header ---------- */
.mf-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(11, 31, 42, .94);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  color: #fff;
  border-bottom: 1px solid rgba(255, 255, 255, .08);
}
.mf-header-inner {
  width: min(var(--maxw), calc(100% - 2.5rem));
  margin-inline: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 64px;
  padding: .4rem 0;
  flex-wrap: wrap;
}
.mf-brand {
  display: flex;
  align-items: center;
  gap: .65rem;
  color: #fff;
  text-decoration: none;
  font-weight: 650;
  font-size: 1.12rem;
  letter-spacing: -.02em;
}
.mf-mark { width: 40px; height: 20px; max-width: 40px; max-height: 20px; flex: 0 0 auto; display: block; }
.mf-nav { display: flex; align-items: center; flex-wrap: wrap; gap: .2rem; }
.mf-nav a {
  color: #CFE0E6;
  text-decoration: none;
  font-size: .92rem;
  font-weight: 560;
  padding: .5rem .85rem;
  border-radius: .5rem;
  transition: color .15s, background .15s;
}
.mf-nav a:hover { color: #fff; background: rgba(255, 255, 255, .08); }
.mf-nav a[aria-current="page"] { color: var(--ink); background: var(--signal-2); }

/* ---------- hero ---------- */
.mf-hero {
  position: relative;
  overflow: hidden;
  background: var(--ink);
  color: #fff;
  text-align: center;
  padding: 3rem 0 4.5rem;
}
.mf-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: radial-gradient(rgba(20, 196, 163, .18) 1.4px, transparent 1.5px);
  background-size: 24px 24px;
  opacity: .5;
  -webkit-mask-image: radial-gradient(ellipse at 50% 20%, #000 25%, transparent 78%);
  mask-image: radial-gradient(ellipse at 50% 20%, #000 25%, transparent 78%);
  pointer-events: none;
}
.mf-hero .mf-wrap { position: relative; z-index: 1; }
.mf-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: .45rem;
  margin: 0 0 .8rem;
  color: var(--signal-2);
  font-family: var(--font-mono);
  font-size: .74rem;
  letter-spacing: .14em;
  text-transform: uppercase;
}
.mf-eyebrow::before {
  content: "";
  width: .45rem;
  height: .45rem;
  border-radius: 99px;
  background: var(--flare);
  box-shadow: 0 0 0 4px rgba(232, 163, 23, .25);
}
.mf-hero h1 {
  margin: 0 auto;
  max-width: 20ch;
  font-size: clamp(2.1rem, 4.6vw, 3.05rem);
  font-weight: 650;
  letter-spacing: -.035em;
  color: #fff;
}
.mf-lede {
  max-width: 46rem;
  margin: .95rem auto 0;
  color: #C9D8DE;
  font-size: 1.05rem;
  line-height: 1.6;
}
.mf-hero-compact { padding-bottom: 4.8rem; }
.mf-hero-chips { display: flex; flex-wrap: wrap; justify-content: center; gap: .5rem; margin-top: 1.35rem; }
.mf-hero-chips span {
  display: inline-flex;
  align-items: center;
  gap: .35rem;
  font-size: .78rem;
  font-weight: 600;
  color: #D6E4E9;
  background: rgba(255, 255, 255, .07);
  border: 1px solid rgba(255, 255, 255, .14);
  padding: .3rem .72rem;
  border-radius: 999px;
}

/* ---------- tool deck ---------- */
.mf-pull { margin-top: -2.8rem; position: relative; z-index: 10; }
.mf-deck {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
}
.mf-deck-bar {
  display: flex;
  flex-wrap: wrap;
  gap: .75rem;
  align-items: center;
  justify-content: space-between;
  padding: .85rem 1.1rem;
  border-bottom: 1px solid var(--line);
  background: linear-gradient(180deg, #fff, #F7FAFB);
}
.mf-modes {
  display: flex;
  flex-wrap: wrap;
  gap: .22rem;
  background: #EDF3F5;
  border: 1px solid var(--line);
  border-radius: .7rem;
  padding: .22rem;
}
.mf-modes button,
.mf-iconbtn {
  border: 0;
  background: transparent;
  color: var(--ink);
  font: inherit;
  font-weight: 600;
  font-size: .88rem;
  min-height: 42px;
  padding: 0 .9rem;
  border-radius: .5rem;
  cursor: pointer;
  transition: background .15s, color .15s;
}
.mf-modes button:hover { background: #E2EBEE; }
.mf-modes button[aria-pressed="true"] { background: var(--ink); color: #fff; box-shadow: 0 4px 12px rgba(11, 31, 42, .22); }
.mf-status { font-family: var(--font-mono); font-size: .73rem; color: var(--muted); letter-spacing: .02em; margin: 0; }

.mf-deck-grid { display: grid; grid-template-columns: 1fr; }
@media (min-width: 900px) {
  .mf-deck-grid { grid-template-columns: 1fr 1fr; }
  .mf-pane + .mf-pane { border-left: 1px solid var(--line); }
}
.mf-pane { padding: 1.1rem 1.1rem .5rem; min-width: 0; }

.mf-label {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: .5rem;
  font-size: .77rem;
  font-weight: 650;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: .5rem;
}
.mf-label span { font-weight: 500; letter-spacing: 0; text-transform: none; }
.mf-input {
  width: 100%;
  min-height: 9.6rem;
  resize: vertical;
  border: 1.5px solid var(--line);
  border-radius: .8rem;
  padding: .85rem .95rem;
  font: inherit;
  color: var(--ink);
  background: #fff;
  line-height: 1.55;
  transition: border-color .15s, box-shadow .15s;
}
.mf-input:focus { outline: none; border-color: var(--signal); box-shadow: 0 0 0 3px rgba(20, 196, 163, .18); }

.mf-chips { display: flex; flex-wrap: wrap; gap: .4rem; margin: .8rem 0 .3rem; }
.mf-chip,
.mf-btn,
.mf-btn-ghost {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink);
  font: inherit;
  font-weight: 600;
  font-size: .88rem;
  min-height: 42px;
  padding: 0 .85rem;
  border-radius: .6rem;
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  text-decoration: none;
  cursor: pointer;
  transition: border-color .15s, background .15s, transform .08s;
}
.mf-chip:hover, .mf-btn:hover, .mf-btn-ghost:hover, .mf-iconbtn:hover { border-color: var(--signal); background: var(--tint-2); }
.mf-chip:active, .mf-btn:active { transform: translateY(1px); }
.mf-btn-primary { background: var(--ink); color: #fff; border-color: var(--ink); }
.mf-btn-primary:hover { background: var(--ink-2); color: #fff; }
.mf-btn-ghost { min-height: 32px; padding: 0 .6rem; font-size: .78rem; color: var(--muted); border-color: var(--line); background: transparent; }

.mf-result {
  min-height: 9.6rem;
  border-radius: .8rem;
  border: 1px solid #1C3A4A;
  background: #0B1B2B;
  color: #E7F6F2;
  padding: .95rem 1rem;
  font-family: var(--font-mono);
  font-size: 1.02rem;
  line-height: 1.75;
  white-space: pre-wrap;
  word-break: break-word;
}
.mf-result:empty::before { content: "The Morse result lands here."; color: rgba(231, 246, 242, .45); font-family: var(--font-sans); font-style: italic; }
.mf-note {
  margin: .55rem 0 0;
  font-size: .86rem;
  color: var(--flare-ink);
  background: var(--warn-bg);
  border: 1px solid var(--warn-line);
  border-radius: .5rem;
  padding: .45rem .65rem;
}

.mf-trace { display: flex; flex-wrap: wrap; align-items: center; gap: 4px; min-height: 1.4rem; margin-top: .7rem; }
.mf-trace i { display: block; height: 7px; border-radius: 99px; background: var(--signal-2); }
.mf-trace i.dit { width: 7px; }
.mf-trace i.dah { width: 20px; }
.mf-trace i.gap { width: 7px; background: transparent; }
.mf-trace i.word { width: 14px; height: 3px; background: var(--flare); }

.mf-map { display: flex; flex-wrap: wrap; gap: .35rem; margin-top: .75rem; }
.mf-pair {
  display: inline-flex;
  align-items: baseline;
  gap: .3rem;
  background: #F2F7F8;
  border: 1px solid var(--line);
  border-radius: .45rem;
  padding: .15rem .45rem;
  font-size: .81rem;
}
.mf-pair b { font-weight: 650; color: var(--ink); }
.mf-pair code { font-family: var(--font-mono); color: var(--signal-ink); }

.mf-audio { display: flex; flex-wrap: wrap; gap: .7rem 1.1rem; align-items: center; padding: .9rem 1.1rem 1rem; }
.mf-deck > .mf-audio { border-top: 1px solid var(--line); background: linear-gradient(180deg, #fff, #F7FAFB); }
.mf-audio.mf-panel { border: 1px solid var(--line); border-radius: .9rem; background: var(--surface); margin: 1rem 0; }
.mf-slider { display: flex; flex-direction: column; gap: .15rem; min-width: 8.5rem; font-size: .72rem; font-weight: 650; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); }
.mf-slider strong { font-family: var(--font-mono); font-size: .85rem; letter-spacing: 0; text-transform: none; color: var(--ink); font-weight: 550; }
.mf-slider input { width: 100%; accent-color: var(--signal); }
.mf-progress { flex-basis: 100%; height: 3px; background: var(--line); border-radius: 99px; overflow: hidden; }
.mf-progress span { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--signal-2), var(--signal)); }
.mf-warn { flex-basis: 100%; margin: 0; font-size: .8rem; color: var(--muted); }

/* ---------- prose ---------- */
.mf-section { margin-top: 3rem; }
.mf-tight { margin-top: 0; }
.mf-panel { border: 1px solid var(--line); border-radius: .9rem; background: var(--surface); box-shadow: var(--shadow); }
.mf-prose { max-width: 760px; margin-inline: auto; }
.mf-prose h2 { margin: 2.2rem 0 .7rem; font-size: 1.5rem; letter-spacing: -.025em; }
.mf-prose h3 { margin: 1.5rem 0 .45rem; font-size: 1.12rem; }
.mf-prose p { margin: 0 0 .95rem; color: var(--body); }
.mf-prose li { color: var(--body); }
.mf-prose a { color: var(--signal-ink); font-weight: 600; }
.mf-prose code {
  font-family: var(--font-mono);
  font-size: .9em;
  background: var(--tint);
  padding: .05em .35em;
  border-radius: .3rem;
  color: var(--ink);
}
.mf-prose ol, .mf-prose ul { padding-left: 1.2rem; margin: .6rem 0 1rem; }
.mf-prose li + li { margin-top: .35rem; }

.mf-steps { list-style: none; padding: 0; margin: 1rem 0 0; display: grid; gap: .7rem; }
.mf-steps li {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: .8rem;
  align-items: start;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: .9rem;
  padding: .9rem 1rem;
  box-shadow: var(--shadow);
}
.mf-step-n { font-family: var(--font-mono); font-size: .8rem; font-weight: 600; color: var(--ink); background: rgba(20, 196, 163, .22); border-radius: .4rem; padding: .2rem .45rem; }

.mf-table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: .9rem; background: #fff; margin: 1rem 0; box-shadow: var(--shadow); }
.mf-table { width: 100%; border-collapse: collapse; font-size: .95rem; }
.mf-table th, .mf-table td { text-align: left; padding: .65rem .85rem; border-bottom: 1px solid var(--line); vertical-align: top; }
.mf-table th { font-size: .72rem; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); background: var(--paper); }
.mf-table tr:last-child td { border-bottom: 0; }
.mf-table code { font-family: var(--font-mono); color: var(--signal-ink); }

.mf-grid-2 { display: grid; gap: .8rem; margin: 1rem 0; }
@media (min-width: 760px) { .mf-grid-2 { grid-template-columns: 1fr 1fr; } }
.mf-card { background: var(--surface); border: 1px solid var(--line); border-radius: .9rem; padding: 1rem 1.05rem; box-shadow: var(--shadow); }
.mf-card h3 { margin: 0 0 .35rem; }
.mf-card p { margin: 0; }

.mf-faq details { background: #fff; border: 1px solid var(--line); border-radius: .75rem; padding: .8rem 1rem; margin-top: .55rem; box-shadow: var(--shadow); }
.mf-faq summary { cursor: pointer; font-weight: 650; color: var(--ink); }
.mf-faq summary:hover { color: var(--signal-ink); }
.mf-faq details p { margin: .55rem 0 0; }

/* ---------- alphabet ---------- */
.mf-alpha { display: grid; grid-template-columns: repeat(auto-fill, minmax(6.8rem, 1fr)); gap: .5rem; margin: .8rem 0 1.2rem; }
.mf-tile {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: .75rem;
  min-height: 4.4rem;
  padding: .55rem .4rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: .1rem;
  font: inherit;
  color: var(--ink);
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: transform .12s, border-color .12s;
}
.mf-tile:hover { transform: translateY(-2px); border-color: var(--signal); }
.mf-tile:active { transform: translateY(0); }
.mf-tile .ch { font-size: 1.3rem; font-weight: 650; }
.mf-tile .cd { font-family: var(--font-mono); color: var(--signal-ink); font-size: .82rem; letter-spacing: .05em; }
.mf-tile[hidden] { display: none; }
.mf-search {
  width: min(100%, 24rem);
  min-height: 44px;
  border: 1px solid var(--line);
  border-radius: .7rem;
  padding: 0 .8rem;
  font: inherit;
  background: #fff;
  display: block;
  margin: .4rem 0 1rem;
}
.mf-search:focus { outline: none; border-color: var(--signal); box-shadow: 0 0 0 3px rgba(20, 196, 163, .16); }

/* ---------- timing bars ---------- */
.mf-timing { display: grid; gap: .45rem; margin: .8rem 0 1rem; }
.mf-barline { display: grid; grid-template-columns: 7.5rem 1fr auto; gap: .6rem; align-items: center; font-size: .86rem; }
.mf-barline span:last-child { font-family: var(--font-mono); color: var(--muted); font-size: .78rem; }
.mf-bar { height: 9px; border-radius: 99px; background: var(--line); overflow: hidden; }
.mf-bar i { display: block; height: 100%; background: var(--signal); border-radius: 99px; }
.mf-bar.flare i { background: var(--flare); }

/* ---------- drill ---------- */
.mf-drill { display: grid; gap: .75rem; }
.mf-choices { display: flex; flex-wrap: wrap; gap: .4rem; }
.mf-score { font-family: var(--font-mono); font-size: .82rem; color: var(--muted); margin: 0; }

/* ---------- footer ---------- */
.mf-footer { margin-top: auto; background: var(--ink); color: rgba(255, 255, 255, .75); padding: 2.2rem 0 1.4rem; font-size: .9rem; }
.mf-footer a { color: var(--signal-2); text-decoration: none; font-weight: 600; }
.mf-footer a:hover { text-decoration: underline; }
.mf-footer-grid { display: flex; flex-wrap: wrap; gap: 1rem 2rem; justify-content: space-between; }
.mf-footer strong { color: #fff; }
.mf-footer-meta { margin-top: 1.2rem; font-family: var(--font-mono); font-size: .72rem; color: rgba(255, 255, 255, .45); }

/* ---------- toast ---------- */
.mf-toast {
  position: fixed;
  bottom: 1.1rem;
  left: 50%;
  transform: translateX(-50%) translateY(.6rem);
  background: var(--ink);
  color: #fff;
  padding: .6rem .95rem;
  border-radius: .6rem;
  border-left: 3px solid var(--signal-2);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  pointer-events: none;
  transition: opacity .2s ease, transform .2s ease;
  z-index: 70;
  font-size: .9rem;
  font-weight: 550;
}
.mf-toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

/* ---------- flashlight ---------- */
.mf-flash.is-on {
  position: fixed;
  inset: 0;
  background: #05080c;
  z-index: 80;
  display: grid !important;
  place-items: center;
  text-align: center;
  padding: 1.5rem;
  color: #fff;
  font-weight: 600;
  font-size: 1.05rem;
  border: 0;
  cursor: pointer;
}
.mf-flash.is-on.lit { background: #F4F7F2; color: var(--ink); }

/* ---------- breadcrumb ---------- */
.mf-crumb { font-size: .85rem; color: var(--muted); margin: 0 0 .9rem; }
.mf-crumb a { color: var(--signal-ink); text-decoration: none; font-weight: 600; }

/* ---------- responsive ---------- */
@media (max-width: 900px) {
  .mf-hero { padding: 2.3rem 0 3.6rem; }
  .mf-hero-compact { padding-bottom: 3.8rem; }
  .mf-hero h1 { font-size: 2rem; }
  .mf-deck-grid { grid-template-columns: 1fr; }
  .mf-pane + .mf-pane { border-left: 0; border-top: 1px solid var(--line); }
  .mf-prose { max-width: none; }
}
@media (max-width: 640px) {
  .mf-wrap, .mf-header-inner { width: calc(100% - 2rem); }
  .mf-header-inner { gap: .4rem; }
  .mf-brand { font-size: 1rem; }
  .mf-mark { width: 34px; height: 17px; }
  .mf-nav a { padding: .45rem .6rem; font-size: .84rem; }
  .mf-deck-bar { padding: .7rem .85rem; }
  .mf-pane { padding: .85rem .85rem .4rem; }
  .mf-audio { gap: .6rem .9rem; padding: .8rem .85rem; }
  .mf-alpha { grid-template-columns: repeat(auto-fill, minmax(5.6rem, 1fr)); }
  .mf-barline { grid-template-columns: 6rem 1fr auto; font-size: .8rem; }
  .mf-footer-grid { flex-direction: column; gap: .8rem; }
  .mf-prose h2 { font-size: 1.35rem; }
}