:root{
  --bg:#f5f7fb;
  --card:#ffffff;
  --accent:#0ea5e9;
  --muted:#475569;
  --text:#0b1220;
  --win:#10b981;
  --lose:#ef4444;
  font-family:Inter, ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
}
html,body{height:100%;}
body{
  margin:0;
  display:flex;
  align-items:center;
  justify-content:center;
  background: #f5f7fb;
  background: linear-gradient(180deg, var(--bg, #f5f7fb), #eef3f8 120%);
  color: var(--text);
  padding:24px;
  box-sizing:border-box;
}
.container{
  width: 90vw;
  max-width: 800px;
  height: auto;
  max-height: calc(100vh - 48px);
  overflow: auto;
  background:var(--card);
  border-radius:12px;
  padding:18px;
  box-shadow: 0 8px 30px rgba(15,23,36,0.06);
  border:1px solid rgba(15,23,36,0.06);
  box-sizing: border-box;
}
header{display:flex;align-items:center;justify-content:space-between;margin-bottom:12px}
h1{font-size:18px;margin:0}
.controls{display:flex;gap:8px;align-items:center}
.board-wrap{
  display: grid;
  grid-template-columns: 1fr minmax(220px, 30%);
  gap: 18px;
}
@media (max-width: 760px) {
  .board-wrap { grid-template-columns: 1fr; gap: 12px; }
  .sidebar { order: 2; }
  .board { order: 1; }
}
.board{
  width:100%;
  max-width: 432px;
  margin: 0 auto;
  aspect-ratio: 1 / 1;
  height: auto;
  display:grid;
  grid-template-columns:repeat(3,1fr);
  grid-template-rows:repeat(3,1fr);
  gap:6px;                     /* smaller gap => visually smaller squares */
  background:linear-gradient(180deg, rgba(10,20,30,0.02), rgba(10,20,30,0.01));
  padding:12px;
  border-radius:10px;
  box-sizing:border-box;
  border:1px solid rgba(15,23,36,0.04);
}
.cell{
  background:linear-gradient(180deg, #fff, #fbfdff);
  display:flex;
  align-items:center;
  justify-content:center;
  font-size: clamp(20px, 4.5vw, 36px);
  line-height: 1;
  font-weight:700;
  border-radius:8px;
  cursor:pointer;
  user-select:none;
  transition: transform .06s ease, box-shadow .12s ease, background .12s ease;
  box-shadow: 0 3px 8px rgba(15,23,36,0.06);
  border:1px solid rgba(15,23,36,0.04);
  color:var(--text);
  padding: 0;
  min-height: 0;
  aspect-ratio: 1 / 1;
}
.cell:hover{ transform: translateY(-3px); }
.cell.disabled{ cursor: default; opacity: 0.9; pointer-events: none; }
.sidebar{
  background:var(--card);
  padding:12px;
  border-radius:10px;
  display:flex;
  flex-direction:column;
  gap:12px;
  min-height:200px;
  border:1px solid rgba(15,23,36,0.04);
}
.status{font-size:14px;color:var(--muted)}
.big{font-size:18px}
.score{display:flex;gap:8px;align-items:center;justify-content:space-between}
.score .box{flex:1;padding:10px;border-radius:8px;background:linear-gradient(180deg,#fbfdff,#f7fbff);text-align:center;border:1px solid rgba(15,23,36,0.03)}
select,input[type=radio]{background:transparent;border:1px solid rgba(15,23,36,0.06);padding:6px;border-radius:6px;color:var(--text)}
button{background:transparent;border:1px solid rgba(15,23,36,0.06);color:var(--text);padding:8px 10px;border-radius:8px;cursor:pointer}
.primary{background:linear-gradient(90deg,var(--accent),#60a5fa);color:#042028;border:none}
.button{background:linear-gradient(90deg,var(--lose),navy);border:none;color:white}
.hint{font-size:13px;color:var(--muted)}
.line-highlight{
  box-shadow:0 0 0 3px rgba(16,185,129,0.12) inset, 0 6px 24px rgba(16,185,129,0.06);
}
footer{display:flex;align-items:center;justify-content:space-between;margin-top:12px;color:var(--muted);font-size:13px}
.icon { width: 64px; height: 64px; margin: 20px; fill: #333; }
.ai-icon { fill: #2a9d8f; }
.game-icon { fill: #264653; }
i { font-size: 23px; color: #2a9d8f; }
.cell:focus { outline: 3px solid rgba(14,165,233,0.15); outline-offset: 2px; }