body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #f0f2f5;
  user-select: none; /* Prevent selection during fast clicking */
}

#game-container {
  width: 100vw;
  height: 100vh;
  position: relative;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

/* UI Panel */
#ui-panel {
  background: white;
  padding: 2rem;
  border-radius: 15px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
  text-align: center;
  z-index: 100;
}

.input-group {
  margin: 10px 0;
  text-align: left;
}

.input-group label {
  display: inline-block;
  width: 150px;
  font-weight: bold;
}

.input-group input[type="number"] {
  padding: 5px;
  border-radius: 5px;
  border: 1px solid #ccc;
  width: 80px;
}

.input-group input[type="checkbox"] {
    transform: scale(1.2);
}

button {
  background-color: #007bff;
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: 5px;
  font-size: 1.1rem;
  cursor: pointer;
  margin-top: 15px;
  transition: background-color 0.2s;
}

button:hover {
  background-color: #0056b3;
}

/* Play Area */
#play-area {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
}

.split-screen {
  width: 50%;
  height: 100%;
  position: relative;
  cursor: pointer;
  background-color: #f8f9fa; /* Uniform background */
  transition: background-color 0.3s;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 8rem; /* For O / X icons */
  font-weight: bold;
}

.split-screen.left {
  border-right: 2px solid #ccc;
}

/* Feedback states */
.correct-feedback {
  background-color: #d4edda !important;
  color: #155724;
}

.wrong-feedback {
  background-color: #f8d7da !important;
  color: #721c24;
}

.split-screen:active {
  background-color: #e2e6ea;
}

/* Squares */
.square {
  position: absolute;
  width: 30px;
  height: 30px;
  background-color: #333;
  border-radius: 4px;
}

/* Result Overlay */
#result-overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(255, 255, 255, 0.95);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  z-index: 200;
}

#result-overlay h2 {
  font-size: 3rem;
  margin-bottom: 20px;
}

#result-overlay p {
  font-size: 2rem;
  color: #333;
}