:root{
  --bg:#ffffff;      /* page background */
  --card:#ffffff;    /* bingo squares */
  --stroke:#d1d5db;  /* borders */
  --text:#111827;    /* main text */
  --muted:#6b7280;   /* helper text */
  --green:#22c55e;   /* marked */
}

*{box-sizing:border-box}

body{
  margin:0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.header{
  padding: 10px 16px 6px;
  display:flex;
  align-items:flex-end;
  justify-content:space-between;
  gap:12px;
  flex-wrap:wrap;
}

.header h1{
  margin:0;
  font-size: 20px;
  letter-spacing: .2px;
}

.sub{
  margin:6px 0 0;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.35;
  max-width: 48ch;
}

.actions{display:flex; gap:8px}

button{
  appearance:none;
  border:1px solid var(--stroke);
  background:transparent;
  color:var(--text);
  padding:10px 12px;
  border-radius:10px;
  font-weight:700;
}

button:active{transform: translateY(1px);}

.wrap{
  padding: 6px 16px 24px;
  display:flex;
  justify-content:center;
}

.board{
  width: min(92vw, 520px);
  aspect-ratio: 1 / 1;
  display:grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 10px;
}

.square{
  background: var(--card);
  border: 1px solid var(--stroke);
  border-radius: 14px;
  display:flex;
  align-items:center;
  justify-content:center;
  padding: 10px;
  position:relative;
  overflow:hidden;
  user-select:none;
  -webkit-tap-highlight-color: transparent;
  transition: transform .08s ease;
}

.square:active{ transform: scale(0.98); }

.square img{
  max-width: 90%;
  max-height: 90%;
  object-fit: contain;
}

.square.marked{
  border-color: rgba(34,197,94,.9);
  box-shadow: 0 0 0 2px rgba(34,197,94,.18) inset;
}

.square.marked::after{
  content:"";
  position:absolute;
  inset:0;
  background: rgba(34,197,94,.22);
}

/* slightly smaller center image, optional polish */
.square img[alt="Halftime"]{
  max-width: 78%;
  max-height: 78%;
}

/* focus ring */
.square:focus-visible{
  outline: 3px solid rgba(17,24,39,.25);
  outline-offset: 2px;
}

/* Bingo banner */
.bingo-banner{
  position: sticky;
  top: 0;
  z-index: 20;
  padding: 10px 16px 0;
}

.bingo-banner__inner{
  width: min(92vw, 520px);
  margin: 0 auto;
  border: 1px solid var(--stroke);
  border-radius: 16px;
  background: #ffffff;
  padding: 10px 12px;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap: 12px;
}

.bingo-banner__title{
  font-weight: 900;
  letter-spacing: .8px;
  font-size: 18px;
  line-height: 1;
}

.bingo-banner__sub{
  color: var(--muted);
  font-size: 12px;
  margin-top: 4px;
}

/* Confetti */
.confetti{
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 50;
  display: none;
}
.confetti.on{
  display: block;
}