body {
  font-family: Arial, sans-serif;
  background: #f5f5f5;
  margin: 0;
  padding: 0;
}
header {
  background: #002244;
  color: white;
  padding: 20px;
  text-align: center;
}
main {
  padding: 20px;
}
.filters {
  margin-bottom: 20px;
}
.problem-card {
  background: white;
  padding: 15px;
  border-radius: 8px;
  margin-bottom: 20px;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
}
pre {
  background: #eee;
  padding: 10px;
  overflow-x: auto;
}