* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;

  display: flex;
  justify-content: center;
  align-items: center;

  font-family: Arial, sans-serif;

  background: #101014;
  color: #ffffff;
}

#play-button {
  position: fixed;
  top: 30px;
  left: 50%;
  transform: translateX(-50%);

  padding: 14px 34px;

  border: 1px solid #3a3a42;
  border-radius: 12px;

  background: #1d1d24;
  color: #ffffff;

  font-size: 17px;
  font-weight: 700;
  letter-spacing: 1px;

  cursor: pointer;

  transition: 0.2s ease;
}

#play-button:hover {
  background: #292931;
  transform: translateX(-50%) translateY(-2px);
}

#board-container {
  display: flex;
  flex-direction: column;
  align-items: center;
}

#score-board {
  margin-bottom: 28px;

  padding: 12px 24px;

  border: 1px solid #303038;
  border-radius: 12px;

  background: #19191f;

  font-size: 20px;
  font-weight: 700;
  letter-spacing: 1px;
}

#score-board:empty {
  display: none;
}

#game-board {
  display: grid;

  grid-template-columns: repeat(3, 150px);
  grid-template-rows: repeat(3, 150px);

  gap: 10px;
}

.square {
  width: 150px;
  height: 150px;

  display: flex;
  justify-content: center;
  align-items: center;

  border: 1px solid #34343d;
  border-radius: 16px;

  background: #19191f;

  font-size: 65px;
  font-weight: 800;

  cursor: pointer;

  transition: 0.15s ease;
}

.square:hover {
  background: #24242c;
  border-color: #555560;
  transform: scale(1.02);
}

#state-message {
  min-height: 30px;

  margin: 25px 0 0;

  font-size: 25px;
  font-weight: 700;
  letter-spacing: 1px;
}

body:has(.popup)::before {
  content: "";

  position: fixed;
  inset: 0;

  z-index: 5;

  background: rgba(0, 0, 0, 0.55);

  backdrop-filter: blur(8px);
}

.popup {
  position: fixed;

  top: 50%;
  left: 50%;

  transform: translate(-50%, -50%);

  z-index: 10;

  min-width: 340px;

  padding: 40px;

  display: flex;
  flex-direction: column;
  align-items: center;

  gap: 16px;

  background: #1b1b22;

  border: 1px solid #3a3a44;
  border-radius: 18px;

  box-shadow: 0 25px 70px rgba(0, 0, 0, 0.65);
}

.popup h2 {
  margin: 0 0 15px;

  font-size: 25px;
}

.popup button {
  width: 130px;

  padding: 13px;

  border: 1px solid #3b3b45;
  border-radius: 10px;

  background: #292931;
  color: #ffffff;

  font-size: 18px;
  font-weight: 700;

  cursor: pointer;

  transition: 0.2s ease;
}

.popup button:hover {
  background: #35353f;
  transform: translateY(-2px);
}