* {
  box-sizing: border-box;
  font-family: "Poppins", sans-serif;
}

body {
  background: linear-gradient(135deg, #ff6b6b, #4ecdc4);
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0;
  color: #fff;
}

.container {
  background: rgba(0, 0, 0, 0.3);
  padding: 30px;
  border-radius: 20px;
  text-align: center;
  width: 400px;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.4);
}

h1 {
  margin-bottom: 15px;
  font-size: 2rem;
  color: #fff;
  text-shadow: 1px 1px 3px rgba(0,0,0,0.5);
}

#game-area {
  margin: 20px 0;
}

#problem {
  font-size: 2rem;
  margin: 20px 0;
  font-weight: bold;
}

input {
  width: 80%;
  padding: 10px;
  font-size: 18px;
  text-align: center;
  border: none;
  border-radius: 8px;
  margin: 10px 0;
}

button {
  background: #2ecc71;
  color: #fff;
  border: none;
  border-radius: 8px;
  padding: 10px 20px;
  font-size: 16px;
  cursor: pointer;
  transition: background 0.3s;
  margin: 5px;
}

button:hover {
  background: #27ae60;
}

#level, #score, #timer {
  font-size: 18px;
  margin: 5px 0;
}

#message {
  margin: 10px 0;
  font-size: 16px;
  min-height: 20px;
}