body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  color: #333;
  max-width: 920px;
  margin: 0 auto;
  padding: 20px;
  background: #f4f4f9;
}

.header {
  text-align: center;
  background: #2c3e50;
  color: white;
  padding: 16px;
  border-radius: 8px;
  margin-bottom: 24px;
}

.timer {
  font-size: 1.4em;
  margin: 12px 0;
  font-weight: bold;
  color: #e74c3c;
}

#student-info {
  font-size: 1.1em;
  margin-top: 8px;
}

.welcome-container {
  text-align: center;
  max-width: 500px;
  margin: 100px auto;
  padding: 40px;
  background: white;
  border-radius: 12px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.15);
}

.form-group {
  margin: 20px 0;
  text-align: left;
}

label {
  display: block;
  margin-bottom: 8px;
  font-weight: 600;
}

input[type="text"] {
  width: 100%;
  padding: 12px;
  font-size: 1.1em;
  border: 2px solid #bdc3c7;
  border-radius: 6px;
  box-sizing: border-box;
}

button {
  padding: 14px 32px;
  font-size: 1.2em;
  font-weight: bold;
  border: none;
  border-radius: 8px;
  cursor: pointer;
}

#startBtn {
  background: #27ae60;
  color: white;
  margin-top: 30px;
}

#startBtn:disabled {
  background: #95a5a6;
  cursor: not-allowed;
}

.question-card {
  background: white;
  padding: 20px;
  margin-bottom: 20px;
  border-radius: 8px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.1);
  border-left: 5px solid #3498db;
}

.question-num {
  font-weight: bold;
  color: #2c3e50;
  font-size: 1.3em;
  margin-bottom: 12px;
}

.math-box {
  background: #ecf0f1;
  padding: 16px;
  margin: 16px 0;
  text-align: center;
  border-radius: 6px;
  border-left: 5px solid #3498db;
}

.check-btn {
  display: block;
  width: 240px;
  margin: 40px auto;
  padding: 14px;
  background: #e67e22;
  color: white;
  font-size: 1.2em;
}

.correct   { background-color: #d5f4e6 !important; border-left-color: #27ae60 !important; }
.incorrect { background-color: #fadbd8 !important; border-left-color: #e74c3c !important; }

#results {
  text-align: center;
  font-size: 2em;
  font-weight: bold;
  padding: 30px;
  background: white;
  border-radius: 12px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.1);
  margin: 40px auto;
  max-width: 700px;
}

.correct-answer-display {
    background: #e8f5e9;
    border: 1px solid #a5d6a7;
    color: #2e7d32;
}

.incorrect .correct-answer-display {
    background: #ffebee;
    border: 1px solid #ef9a9a;
    color: #c62828;
}

.correct-answer-display strong {
    color: inherit;
}