:root {
  font-family: Arial, Helvetica, sans-serif;
  color: #111;
  background-color: #f4f4f6;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
}

.app {
  width: min(92vw, 420px);
  padding: 2rem;
  background: #fff;
  border: 1px solid #ddd;
  border-radius: 14px;
  box-shadow: 0 10px 26px rgba(0, 0, 0, 0.08);
  display: grid;
  gap: 1rem;
  justify-items: center;
}

h1 {
  margin: 0;
  font-size: 1.9rem;
}

.status {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 600;
  color: #333;
}

.scoreboard {
  margin: 0;
  font-size: 1rem;
  font-weight: 600;
  color: #444;
}

.board {
  width: 100%;
  max-width: 300px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.6rem;
}

.cell {
  aspect-ratio: 1 / 1;
  border: 2px solid #c9c9c9;
  border-radius: 10px;
  background: #fafafa;
  font-size: clamp(2rem, 5vw, 2.4rem);
  font-weight: 700;
  color: #1a1a1a;
  cursor: pointer;
  transition: background-color 120ms ease, border-color 120ms ease, box-shadow 120ms ease;
}

.cell:hover {
  background: #f1f1f1;
}

.cell:focus-visible {
  outline: 3px solid #6ea8ff;
  outline-offset: 2px;
}

.cell--winner {
  background: #dcfce7;
  border-color: #22c55e;
  box-shadow: 0 0 0 1px #22c55e;
}

.actions {
  width: 100%;
  display: grid;
  gap: 0.6rem;
}

.reset-btn {
  border: none;
  border-radius: 10px;
  padding: 0.75rem 1.2rem;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  background: #2563eb;
  color: #fff;
}

.reset-btn:hover {
  background: #1e4fbd;
}

.reset-btn--secondary {
  background: #4b5563;
}

.reset-btn--secondary:hover {
  background: #374151;
}

.mode-selector {
  width: 100%;
  border: 1px solid #ddd;
  border-radius: 10px;
  padding: 0.75rem 0.9rem;
  margin: 0;
  display: grid;
  gap: 0.4rem;
}

.mode-selector legend {
  padding: 0 0.3rem;
  font-weight: 700;
  color: #333;
}

.mode-selector label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
  color: #444;
}

.difficulty-selector {
  width: 100%;
  display: grid;
  gap: 0.45rem;
  font-weight: 700;
  color: #333;
}

.difficulty-selector select {
  border: 1px solid #d1d5db;
  border-radius: 8px;
  padding: 0.55rem 0.65rem;
  font-size: 1rem;
  background: #fff;
  color: #111;
}

.difficulty-selector select:disabled {
  background: #f3f4f6;
  color: #6b7280;
  cursor: not-allowed;
}