* { margin: 0; padding: 0; box-sizing: border-box; }
body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
  color: #fff;
  min-height: 100vh;
}
.app {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 20px;
}
.card {
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.15);
  border-radius: 16px;
  padding: 32px;
  width: 100%;
  max-width: 420px;
  backdrop-filter: blur(10px);
}
h1 { text-align: center; margin-bottom: 8px; color: #00d4ff; }
.subtitle { text-align: center; color: #a0a0c0; margin-bottom: 24px; }
.input-group { margin-bottom: 16px; }
.input-group label { display: block; margin-bottom: 6px; font-size: 14px; color: #c0c0d0; }
.input-group input {
  width: 100%; padding: 12px 14px;
  border: 1px solid rgba(255,255,255,0.2);
  border-radius: 10px;
  background: rgba(0,0,0,0.25);
  color: #fff; font-size: 16px; outline: none;
}
.input-group input:focus { border-color: #00d4ff; }
.btn {
  width: 100%; padding: 14px; border: none; border-radius: 10px;
  background: linear-gradient(90deg, #00d4ff, #0099cc);
  color: #fff; font-size: 16px; font-weight: 600; cursor: pointer;
}
.btn:hover { opacity: 0.92; }
.btn:disabled { opacity: 0.6; cursor: not-allowed; }
.subjects { display: grid; gap: 16px; width: 100%; max-width: 480px; }
.subject-card {
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.15);
  border-radius: 16px;
  padding: 24px; cursor: pointer;
}
.subject-card:hover { background: rgba(255,255,255,0.13); }
.subject-card h2 { color: #00d4ff; margin-bottom: 8px; }
.subject-card p { color: #a0a0c0; font-size: 14px; }
.quiz-header {
  width: 100%; max-width: 720px;
  display: flex; justify-content: space-between; align-items: center;
  margin-bottom: 20px;
}
.quiz-header h2 { color: #00d4ff; }
.quiz-card {
  width: 100%; max-width: 720px;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.15);
  border-radius: 16px;
  padding: 24px; margin-bottom: 16px;
}
.question-number { color: #00d4ff; font-size: 14px; margin-bottom: 12px; }
.question-text { font-size: 18px; margin-bottom: 20px; line-height: 1.5; }
.options { display: grid; gap: 12px; }
.option {
  padding: 14px;
  border: 1px solid rgba(255,255,255,0.2);
  border-radius: 10px;
  background: rgba(0,0,0,0.2);
  cursor: pointer;
}
.option:hover { background: rgba(255,255,255,0.1); }
.option.selected { border-color: #00d4ff; background: rgba(0,212,255,0.15); }
.option.correct { border-color: #2ecc71; background: rgba(46,204,113,0.2); }
.option.wrong { border-color: #e74c3c; background: rgba(231,76,60,0.2); }
.result-card {
  width: 100%; max-width: 720px; text-align: center;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.15);
  border-radius: 16px; padding: 32px;
}
.result-card h2 { color: #00d4ff; margin-bottom: 16px; }
.result-score { font-size: 48px; font-weight: 700; margin: 16px 0; }
.actions { display: flex; gap: 12px; margin-top: 24px; }
.actions .btn { flex: 1; }
.btn-secondary { background: rgba(255,255,255,0.15); }
.error { color: #ff6b6b; text-align: center; margin-top: 12px; font-size: 14px; }
.progress-bar {
  width: 100%; height: 8px;
  background: rgba(255,255,255,0.1);
  border-radius: 4px; margin-bottom: 20px; overflow: hidden;
}
.progress-fill { height: 100%; background: linear-gradient(90deg, #00d4ff, #0099cc); }
.header-bar {
  position: fixed; top: 0; left: 0; right: 0;
  padding: 16px 20px;
  display: flex; justify-content: space-between; align-items: center;
  background: rgba(0,0,0,0.25);
  border-bottom: 1px solid rgba(255,255,255,0.1);
}
.header-bar h3 { color: #00d4ff; }
.logout {
  background: transparent; border: 1px solid rgba(255,255,255,0.3);
  color: #fff; padding: 8px 14px; border-radius: 8px; cursor: pointer;
}
.logout:hover { background: rgba(255,255,255,0.1); }
.empty { text-align: center; color: #a0a0c0; margin-top: 40px; }