/* ===== Brand tokens (doc/DESIGN.md) ===== */
:root {
  /* Brand palette */
  --color-primary: #0B1F3A;
  --color-primary-hover: #123E66;
  --color-secondary: #18B7C9;
  --color-secondary-hover: #38D5E8;
  --color-accent: #F5B84B;
  --color-accent-hover: #F7C96D;
  --color-bg: #F8FAFC;
  --color-surface: #E6EDF3;
  --color-text: #1E293B;
  --color-text-muted: #64748B;
  --color-bg-dark: #071426;
  --color-success: #22C55E;
  --color-warning: #F59E0B;
  --color-error: #EF4444;

  /* App aliases */
  --bg: var(--color-bg);
  --panel: #FFFFFF;
  --text: var(--color-text);
  --muted: var(--color-text-muted);
  --line: #C5D0DB;
  --line-bold: var(--color-primary);
  --given: var(--color-primary);
  --user: var(--color-primary-hover); /* navy-blue; readable on white (avoid cyan body text) */
  --cell-bg: #FFFFFF;
  --peer: #E4F6F9;           /* row/col/box assist */
  --same: #C8EEF4;           /* same-value highlight */
  --selected: #A8E6EF;       /* selected cell */
  --conflict: #FEE2E2;
  --conflict-text: var(--color-error);
  --accent: var(--color-secondary);
  --accent-strong: var(--color-primary);
  --cta: var(--color-accent);
  --cta-hover: var(--color-accent-hover);
  --cta-text: var(--color-primary);
  --btn: var(--color-surface);
  --btn-hover: #D7E2EB;
  --cand: var(--color-success);
  --cand-soft: #DCFCE7;
  --shadow: 0 10px 30px rgba(11, 31, 58, 0.10);
  --shadow-soft: 0 18px 45px rgba(11, 31, 58, 0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --focus-ring: 0 0 0 3px rgba(24, 183, 201, 0.35);

  --font-heading: "Montserrat", "Noto Sans SC", "Source Han Sans TC", sans-serif;
  --font-body: "Inter", "Noto Sans SC", "Source Han Sans TC", sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, monospace;
}

/* Dark mode (DESIGN §12.2) */
body.dark {
  --bg: var(--color-bg-dark);
  --panel: var(--color-primary);
  --text: #E6EDF3;
  --muted: #94A3B8;
  --line: #1E3A55;
  --line-bold: #38D5E8;
  --given: #F8FAFC;
  --user: #38D5E8;
  --cell-bg: #0B1F3A;
  --peer: #0F2A45;
  --same: #164A5C;
  --selected: #1A5F72;
  --conflict: #5A2530;
  --conflict-text: #FF8A8A;
  --accent: #38D5E8;
  --accent-strong: #F8FAFC;
  --cta: var(--color-accent);
  --cta-hover: var(--color-accent-hover);
  --cta-text: var(--color-primary);
  --btn: #123E66;
  --btn-hover: #1A4F7A;
  --cand: #4ADE80;
  --cand-soft: #14532D;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.45);
  --shadow-soft: 0 18px 45px rgba(0, 0, 0, 0.5);
  --focus-ring: 0 0 0 3px rgba(56, 213, 232, 0.4);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  -webkit-tap-highlight-color: transparent;
  transition: background .25s, color .25s;
}

.app {
  max-width: 520px;
  margin: 0 auto;
  padding: 16px 14px 40px;
}

.main { display: block; }

/* SEO/GEO: short product intro (visible, factual) */
.intro-blurb {
  margin: 16px 0 0;
  padding: 10px 12px;
  font-size: 0.8125rem;
  line-height: 1.55;
  color: var(--muted);
  background: var(--color-surface);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--color-secondary);
}
body.dark .intro-blurb {
  background: rgba(11, 31, 58, 0.85);
  border-left-color: var(--color-secondary-hover);
}
.intro-blurb strong {
  color: var(--text);
  font-weight: 600;
}

/* FAQ (crawlable; collapsed by default) */
.faq {
  margin-top: 20px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
}
.faq-heading {
  font-family: var(--font-heading);
  font-size: 0.9375rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 10px;
  color: var(--accent-strong);
}
body.dark .faq-heading { color: #F8FAFC; }
.faq-item {
  margin-bottom: 6px;
  padding: 8px 10px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  font-size: 0.8125rem;
  color: var(--text);
}
.faq-item summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--text);
  list-style-position: outside;
}
.faq-item summary:hover { color: var(--color-secondary); }
body.dark .faq-item summary:hover { color: var(--color-secondary-hover); }
.faq-item p {
  margin: 8px 0 2px;
  color: var(--muted);
  line-height: 1.55;
}
.faq-item strong { color: var(--text); font-weight: 600; }

/* ===== Top bar ===== */
.topbar {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 12px;
  padding: 12px 14px;
  background: var(--color-primary);
  color: #F8FAFC;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
}
body.dark .topbar {
  background: linear-gradient(135deg, #0B1F3A 0%, #123E66 55%, #0E4A58 100%);
  border: 1px solid rgba(56, 213, 232, 0.2);
}
.topbar h1 {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0;
  flex: 1 1 auto;
  color: #F8FAFC;
}
.topbar .info {
  display: flex;
  align-items: center;
  gap: 10px;
  color: #E6EDF3;
}
#timer {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 1.05rem;
  font-weight: 600;
  min-width: 52px;
  text-align: center;
  color: var(--color-accent);
}
#mistakes {
  font-size: 0.8125rem;
  font-weight: 500;
  color: #FCA5A5;
  min-width: 0;
}

/* Shared control chrome */
select,
.ctrl-btn,
.pad-btn,
.icon-btn,
.mode-btn {
  font-family: inherit;
  cursor: pointer;
  border: 1px solid var(--line);
  background: var(--panel);
  color: var(--text);
  border-radius: var(--radius-sm);
}

select:focus-visible,
.ctrl-btn:focus-visible,
.pad-btn:focus-visible,
.icon-btn:focus-visible,
.mode-btn:focus-visible,
.cell:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

/* Settings strip */
.settings {
  display: flex;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 14px;
  padding: 10px 12px;
  font-size: 0.8125rem;
  color: var(--muted);
  background: var(--color-surface);
  border-radius: var(--radius-md);
  border: 1px solid transparent;
}
body.dark .settings {
  background: rgba(11, 31, 58, 0.85);
  border-color: rgba(56, 213, 232, 0.12);
}
.settings label {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
  user-select: none;
}
.settings select {
  padding: 6px 8px;
  font-size: 0.8125rem;
  background: var(--panel);
  border-color: var(--line);
  color: var(--text);
}
.settings input[type="checkbox"] {
  accent-color: var(--color-secondary);
  width: 1rem;
  height: 1rem;
}
.icon-btn {
  padding: 6px 12px;
  font-size: 0.8125rem;
  font-weight: 600;
  background: rgba(248, 250, 252, 0.12);
  border-color: rgba(248, 250, 252, 0.22);
  color: #F8FAFC;
  transition: background .15s, border-color .15s;
}
.icon-btn:hover {
  background: rgba(248, 250, 252, 0.2);
  border-color: var(--color-accent);
}
.icon-btn:active { transform: scale(.97); }

/* ===== Board ===== */
.board-wrap {
  position: relative;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow);
}

#board {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  aspect-ratio: 1 / 1;
  width: 100%;
  background: var(--line-bold);
  border: 3px solid var(--line-bold);
  border-radius: var(--radius-md);
  overflow: hidden;
  touch-action: manipulation;
}

.cell {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--cell-bg);
  border: 0;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  font-family: var(--font-body);
  font-size: clamp(18px, 6vw, 30px);
  font-weight: 500;
  font-variant-numeric: tabular-nums;
  color: var(--user);
  padding: 0;
  transition: background .12s;
  user-select: none;
}
/* 3x3 box bold edges */
.cell.bl { border-left: 2px solid var(--line-bold); }
.cell.bt { border-top: 2px solid var(--line-bold); }
.cell.bl:not(.br) { margin-left: -1px; }

.cell.given {
  color: var(--given);
  font-weight: 700;
}
.cell.user { color: var(--user); }

/* Highlight layers (later rules win) */
.cell.peer { background: var(--peer); }
.cell.same { background: var(--same); }
.cell.conflict { background: var(--conflict); color: var(--conflict-text); }
.cell.selected {
  background: var(--selected);
  box-shadow: inset 0 0 0 2px var(--accent);
  z-index: 1;
}
/* Color-blind friendly conflict cue */
.cell.conflict::after {
  content: "";
  position: absolute;
  left: 18%; right: 18%; bottom: 14%;
  border-bottom: 2px dotted var(--conflict-text);
}
.cell.flash-error {
  animation: flash 0.4s ease-in-out 0s 3;
}
@keyframes flash {
  0%, 100% { background: var(--cell-bg); }
  50% { background: var(--conflict); }
}

/* ===== Pause overlay ===== */
.overlay {
  position: absolute;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 8px;
  background: rgba(7, 20, 38, 0.88);
  color: #F8FAFC;
  border-radius: var(--radius-md);
  font-family: var(--font-heading);
  font-size: 1.125rem;
  font-weight: 600;
  cursor: pointer;
  z-index: 5;
  backdrop-filter: blur(2px);
}
.overlay.show { display: flex; }
.overlay .hint {
  font-family: var(--font-body);
  font-size: 0.8125rem;
  font-weight: 400;
  opacity: .85;
  color: #E6EDF3;
}

/* ===== Candidate micro-grid ===== */
.cand {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  font-style: normal;
}
.cand i {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(8px, 2.3vw, 12px);
  font-weight: 600;
  line-height: 1;
  color: var(--cand);
  font-style: normal;
  font-variant-numeric: tabular-nums;
}

/* ===== Number pad + mode toggle ===== */
.pad-row {
  display: flex;
  gap: 8px;
  margin-top: 14px;
  align-items: stretch;
}
#numpad {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 6px;
  flex: 1 1 auto;
}

.mode-btn {
  flex: 0 0 auto;
  width: 64px;
  font-size: 0.8125rem;
  font-weight: 600;
  line-height: 1.25;
  padding: 4px 6px;
  color: var(--text);
  background: var(--btn);
  transition: background .15s, color .15s, border-color .15s;
}
.mode-btn:hover {
  background: var(--btn-hover);
}
.mode-btn.on {
  background: var(--cand);
  color: #fff;
  border-color: var(--cand);
}

/* Notes mode: green pad theme (FR-C02) */
body.candidate-mode .pad-btn {
  color: var(--cand);
  border-color: var(--cand);
}
body.candidate-mode .pad-btn.active {
  background: var(--cand-soft);
}
body.candidate-mode .pad-btn.disabled {
  color: var(--muted);
  border-color: var(--line);
}

.pad-btn {
  position: relative;
  aspect-ratio: 1 / 1.15;
  font-size: clamp(18px, 5.5vw, 26px);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  color: var(--color-primary);
  background: var(--panel);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: transform .08s, background .15s, border-color .15s;
  box-shadow: 0 1px 2px rgba(11, 31, 58, 0.06);
}
body.dark .pad-btn {
  color: var(--color-secondary-hover);
}
.pad-btn:hover:not(.disabled) {
  border-color: var(--accent);
}
.pad-btn:active:not(.disabled) { transform: scale(.94); }
.pad-btn.active {
  background: var(--same);
  border-color: var(--accent);
}
.pad-btn.disabled {
  color: var(--muted);
  opacity: .4;
  cursor: not-allowed;
  background: var(--btn);
  box-shadow: none;
}
/* Remaining count badge */
.pad-btn::after {
  content: attr(data-remain);
  position: absolute;
  top: 3px;
  right: 5px;
  font-size: 10px;
  font-weight: 500;
  color: var(--muted);
}
.pad-btn.disabled::after { content: ""; }

/* ===== Controls ===== */
.controls {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin-top: 14px;
}
.ctrl-btn {
  padding: 10px 8px;
  font-size: 0.875rem;
  font-weight: 600;
  background: var(--btn);
  border-color: var(--line);
  color: var(--text);
  transition: transform .08s, background .15s, border-color .15s, color .15s;
}
.ctrl-btn:hover {
  background: var(--btn-hover);
}
.ctrl-btn:active { transform: scale(.97); }

/* Primary action = CTA gold on navy (DESIGN §13) */
.ctrl-btn.primary {
  background: var(--cta);
  color: var(--cta-text);
  border-color: var(--cta);
  font-weight: 700;
}
.ctrl-btn.primary:hover {
  background: var(--cta-hover);
  border-color: var(--cta-hover);
}

/* Secondary-style for Check (cyan) */
#checkBtn {
  border-color: var(--color-secondary);
  color: var(--color-primary);
  background: rgba(24, 183, 201, 0.12);
}
body.dark #checkBtn {
  color: var(--color-secondary-hover);
  background: rgba(24, 183, 201, 0.15);
  border-color: rgba(56, 213, 232, 0.45);
}
#checkBtn:hover {
  background: rgba(24, 183, 201, 0.22);
}

/* Status message box */
.status-box {
  margin-top: 12px;
  padding: 10px 12px;
  background: var(--color-surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  box-shadow: 0 1px 2px rgba(11, 31, 58, 0.04);
  text-align: left;
}
body.dark .status-box {
  background: rgba(11, 31, 58, 0.9);
  border-color: rgba(56, 213, 232, 0.18);
}
.status-label {
  display: block;
  font-family: var(--font-heading);
  font-size: 0.6875rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-secondary);
  margin-bottom: 4px;
}
body.dark .status-label {
  color: var(--color-secondary-hover);
}
#status {
  min-height: 1.35em;
  font-size: 0.8125rem;
  line-height: 1.45;
  color: var(--text);
  text-align: left;
}
#status:empty::before {
  content: "Ready";
  color: var(--muted);
  font-style: italic;
}
.status-box.is-error #status {
  color: var(--conflict-text);
}
.status-box.is-success #status {
  color: var(--color-success);
}
body.dark .status-box.is-success #status {
  color: var(--cand);
}

/* ===== Modals ===== */
.modal {
  position: fixed;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  background: rgba(7, 20, 38, 0.55);
  z-index: 20;
  padding: 20px;
  backdrop-filter: blur(3px);
}
.modal.show { display: flex; }
.modal-card {
  background: var(--panel);
  color: var(--text);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
  width: 100%;
  max-width: 340px;
  box-shadow: var(--shadow-soft);
  text-align: center;
  border: 1px solid rgba(11, 31, 58, 0.06);
}
body.dark .modal-card {
  border-color: rgba(56, 213, 232, 0.15);
}
.modal-card h2 {
  font-family: var(--font-heading);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 12px;
  color: var(--accent-strong);
}
body.dark .modal-card h2 {
  color: #F8FAFC;
}
.modal-card .stats {
  margin: 12px 0 20px;
  line-height: 1.9;
  font-size: 0.9375rem;
  color: var(--muted);
}
.modal-card .stats b {
  color: var(--color-secondary);
  font-weight: 700;
}
body.dark .modal-card .stats b {
  color: var(--color-secondary-hover);
}
.modal-actions { display: flex; gap: 10px; }
.modal-actions .ctrl-btn { flex: 1; }

/* ===== Reduced motion ===== */
@media (prefers-reduced-motion: reduce) {
  body,
  .cell,
  .pad-btn,
  .ctrl-btn,
  .mode-btn,
  .icon-btn {
    transition: none;
  }
  .cell.flash-error {
    animation: none;
    background: var(--conflict);
  }
  .pad-btn:active,
  .ctrl-btn:active,
  .icon-btn:active {
    transform: none;
  }
}

/* ===== Landscape ===== */
@media (min-width: 760px) and (orientation: landscape) {
  .app { max-width: 900px; }
}