/* ── LIGHT THEME ──────────────────────────────────────────────────────────── */
:root {
  --bg:            #f1f5f9;
  --surface:       #ffffff;
  --border:        #e2e8f0;
  --border-hi:     #c7d2fe;
  --accent:        #6d28d9;
  --accent-hi:     #5b21b6;
  --accent-lo:     #ede9fe;
  --text:          #0f172a;
  --text-muted:    #475569;
  --text-dim:      #94a3b8;
  --mark-color:    rgba(109, 40, 217, 0.18);
  --mark-border:   rgba(109, 40, 217, 0.6);
  --mark-bg:       rgba(109, 40, 217, 0.08);
  --cell-hover:    #f5f3ff;
  --cell-free-bg:  #ede9fe;
  --cell-free-border: #7c3aed;
  --cell-free-text:   #5b21b6;
  --header-bg:     linear-gradient(135deg, #7c3aed 0%, #4c1d95 100%);
  --header-text:   #ffffff;
  --header-sub:    rgba(255,255,255,0.7);
  --btn-outline-border: #6d28d9;
  --btn-outline-text:   #6d28d9;
  --btn-outline-hover:  #ede9fe;
  --btn-regen-bg:  #ef4444;
  --btn-regen-hi:  #dc2626;
  --shadow-sm:     0 1px 3px rgba(0,0,0,0.07), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md:     0 4px 16px rgba(0,0,0,0.08), 0 2px 6px rgba(0,0,0,0.05);
  --shadow-cell:   0 1px 4px rgba(0,0,0,0.06);
  --shadow-cell-hover: 0 4px 12px rgba(109,40,217,0.15);
  --radius:        10px;
}

/* ── DARK THEME ───────────────────────────────────────────────────────────── */
[data-theme="dark"] {
  --bg:            #0d0d1a;
  --surface:       #1a1a2e;
  --border:        #2d2d50;
  --border-hi:     #4338ca;
  --accent:        #a78bfa;
  --accent-hi:     #c4b5fd;
  --accent-lo:     #2d1b69;
  --text:          #e2e8f0;
  --text-muted:    #94a3b8;
  --text-dim:      #475569;
  --mark-color:    rgba(167, 139, 250, 0.22);
  --mark-border:   rgba(167, 139, 250, 0.65);
  --mark-bg:       rgba(167, 139, 250, 0.06);
  --cell-hover:    rgba(167, 139, 250, 0.07);
  --cell-free-bg:  rgba(109, 40, 217, 0.22);
  --cell-free-border: #7c3aed;
  --cell-free-text:   #c4b5fd;
  --header-bg:     linear-gradient(135deg, #3b0764 0%, #1e1b4b 100%);
  --header-text:   #f5f3ff;
  --header-sub:    rgba(245,243,255,0.55);
  --btn-outline-border: #a78bfa;
  --btn-outline-text:   #a78bfa;
  --btn-outline-hover:  rgba(167, 139, 250, 0.1);
  --btn-regen-bg:  #b91c1c;
  --btn-regen-hi:  #991b1b;
  --shadow-sm:     0 1px 3px rgba(0,0,0,0.4), 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md:     0 4px 16px rgba(0,0,0,0.5), 0 2px 6px rgba(0,0,0,0.4);
  --shadow-cell:   0 1px 4px rgba(0,0,0,0.35);
  --shadow-cell-hover: 0 4px 12px rgba(0,0,0,0.5);
  --radius:        10px;
}

/* ── SYSTEM DARK FALLBACK ─────────────────────────────────────────────────── */
@media (prefers-color-scheme: dark) {
  html:not([data-theme]) {
    --bg:            #0d0d1a;
    --surface:       #1a1a2e;
    --border:        #2d2d50;
    --border-hi:     #4338ca;
    --accent:        #a78bfa;
    --accent-hi:     #c4b5fd;
    --accent-lo:     #2d1b69;
    --text:          #e2e8f0;
    --text-muted:    #94a3b8;
    --text-dim:      #475569;
    --mark-color:    rgba(167, 139, 250, 0.22);
    --mark-border:   rgba(167, 139, 250, 0.65);
    --mark-bg:       rgba(167, 139, 250, 0.06);
    --cell-hover:    rgba(167, 139, 250, 0.07);
    --cell-free-bg:  rgba(109, 40, 217, 0.22);
    --cell-free-border: #7c3aed;
    --cell-free-text:   #c4b5fd;
    --header-bg:     linear-gradient(135deg, #3b0764 0%, #1e1b4b 100%);
    --header-text:   #f5f3ff;
    --header-sub:    rgba(245,243,255,0.55);
    --btn-outline-border: #a78bfa;
    --btn-outline-text:   #a78bfa;
    --btn-outline-hover:  rgba(167, 139, 250, 0.1);
    --btn-regen-bg:  #b91c1c;
    --btn-regen-hi:  #991b1b;
    --shadow-sm:     0 1px 3px rgba(0,0,0,0.4), 0 1px 2px rgba(0,0,0,0.3);
    --shadow-md:     0 4px 16px rgba(0,0,0,0.5), 0 2px 6px rgba(0,0,0,0.4);
    --shadow-cell:   0 1px 4px rgba(0,0,0,0.35);
    --shadow-cell-hover: 0 4px 12px rgba(0,0,0,0.5);
    --radius:        10px;
  }
}

/* ── RESET & BASE ───────────────────────────────────────────────────────────  */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Inter', system-ui, sans-serif;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background 0.25s, color 0.25s;
}

/* ── SITE HEADER ────────────────────────────────────────────────────────────  */
.site-header {
  background: var(--header-bg);
  padding: 28px 24px 24px;
  text-align: center;
}

.site-title h1 {
  font-family: 'Outfit', system-ui, sans-serif;
  font-size: clamp(1.8rem, 5vw, 3rem);
  font-weight: 800;
  color: var(--header-text);
  letter-spacing: -0.02em;
}

.tagline {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.15em;
  color: var(--header-sub);
  margin-top: 6px;
  text-transform: uppercase;
}

/* ── CONTROLS BAR ───────────────────────────────────────────────────────────  */
.controls-bar {
  display: flex;
  justify-content: center;
  gap: 10px;
  padding: 14px 20px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
  box-shadow: var(--shadow-sm);
}

.btn-control {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  padding: 8px 20px;
  border-radius: 9999px;
  border: 1.5px solid var(--btn-outline-border);
  background: transparent;
  color: var(--btn-outline-text);
  cursor: pointer;
  transition: background 0.15s, box-shadow 0.15s, transform 0.1s;
}

.btn-control:hover {
  background: var(--btn-outline-hover);
  box-shadow: var(--shadow-sm);
}

.btn-control:active {
  transform: scale(0.97);
}

.btn-control:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.btn-danger {
  background: var(--btn-regen-bg);
  border-color: var(--btn-regen-bg);
  color: #fff;
}

.btn-danger:hover {
  background: var(--btn-regen-hi);
  border-color: var(--btn-regen-hi);
}

/* ── MAIN WRAPPER ───────────────────────────────────────────────────────────  */
.wrapper {
  flex: 1;
  padding: 24px 16px 36px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

/* ── BINGO HEADER ROW (B I N G O) ──────────────────────────────────────────  */
.bingo-header {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
  width: 100%;
  max-width: 820px;
  margin-bottom: 8px;
}

.bingo-letter {
  display: flex;
  align-items: center;
  justify-content: center;
  aspect-ratio: 1 / 1;
  font-family: 'Outfit', system-ui, sans-serif;
  font-size: clamp(1.4rem, 3.5vw, 2.2rem);
  font-weight: 800;
  color: var(--accent);
  letter-spacing: -0.02em;
}

/* ── BINGO GRID ─────────────────────────────────────────────────────────────  */
.bingo-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
  width: 100%;
  max-width: 820px;
}

.bingo-cell {
  aspect-ratio: 1 / 1;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 10px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  cursor: pointer;
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 1rem; /* overridden per-cell by fitCellText() */
  font-weight: 500;
  line-height: 1.2;
  color: var(--text);
  overflow: hidden;
  box-shadow: var(--shadow-cell);
  transition: background 0.15s, border-color 0.15s, box-shadow 0.15s, transform 0.1s;
  user-select: none;
}

.bingo-cell:hover:not(.free) {
  background: var(--cell-hover);
  border-color: var(--border-hi);
  box-shadow: var(--shadow-cell-hover);
  transform: translateY(-1px);
}

.bingo-cell:active:not(.free) {
  transform: translateY(0);
}

.bingo-cell:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: -2px;
  z-index: 1;
}

.bingo-cell.free {
  background: var(--cell-free-bg);
  border-color: var(--cell-free-border);
  cursor: default;
  font-weight: 700;
  font-style: italic;
  color: var(--cell-free-text);
}

.cell-text {
  display: block;
  width: 100%;
  text-align: center;
  line-height: 1.2;
  position: relative;
  z-index: 1;
  pointer-events: none;
}

/* ── MARK OVERLAY ───────────────────────────────────────────────────────────  */
.mark {
  position: absolute;
  inset: 10%;
  border-radius: 50%;
  background: var(--mark-color);
  border: 2.5px solid var(--mark-border);
  opacity: 0;
  transform: scale(0.4);
  transition: opacity 0.18s ease, transform 0.18s cubic-bezier(0.34, 1.56, 0.64, 1);
  pointer-events: none;
  z-index: 2;
}

.bingo-cell.marked .mark {
  opacity: 1;
  transform: scale(1);
}

/* ── BINGO WIN ANNOUNCEMENT ─────────────────────────────────────────────────  */
.bingo-announcement {
  margin-top: 24px;
  padding: 16px 36px;
  border-radius: 9999px;
  background: var(--accent);
  font-family: 'Outfit', system-ui, sans-serif;
  font-size: clamp(1.2rem, 3.5vw, 1.8rem);
  font-weight: 800;
  color: #fff;
  letter-spacing: 0.1em;
  text-align: center;
  box-shadow: var(--shadow-md);
  animation: pop-breathe 2s ease-in-out infinite;
}

@keyframes pop-breathe {
  0%, 100% { transform: scale(1);    box-shadow: var(--shadow-md); }
  50%       { transform: scale(1.03); box-shadow: 0 8px 24px rgba(109,40,217,0.35); }
}

/* ── RESPONSIVE ─────────────────────────────────────────────────────────────  */
@media (max-width: 540px) {
  .bingo-cell {
    padding: 5px;
    font-size: 0.55rem;
    border-radius: 7px;
  }

  .bingo-header,
  .bingo-grid {
    gap: 5px;
  }

  .controls-bar {
    flex-direction: column;
    align-items: center;
  }

  .btn-control {
    width: 100%;
    max-width: 280px;
    text-align: center;
  }
}