* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: 'Segoe UI', sans-serif;
  background: #f4f4f4;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.site-header {
  position: fixed;
  top: 0;
  width: 100%;
  background-color: #2c3e50;
  color: white;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 15px 20px;
  z-index: 1000;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
}

.site-title {
  margin: 0;
  font-size: 1.5rem;
}

.level-btn {
  background-color: #6a0dad;
  color: white;
  border: none;
  padding: 10px 20px;
  font-size: 0.95rem;
  border-radius: 4px;
  cursor: pointer;
  transition: 0.3s ease;
}

.level-btn:hover {
  background-color: #4b0082;
  transform: scale(1.05);
}

main {
  padding: 100px 20px 40px; /* space for fixed header */
  flex: 1;
}

.level {
  margin-bottom: 40px;
}

.level h2 {
  text-align: center;
  margin-bottom: 20px;
  color: #333;
}

.tiles {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 15px;
}

.tile {
  background-color: white;
  padding: 20px;
  width: 160px;
  text-align: center;
  border-radius: 8px;
  text-decoration: none;
  color: #333;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
  transition: 0.3s;
}

.tile:hover {
  background-color: #e6f2ff;
  transform: scale(1.03);
}

.site-footer {
  background: #333;
  color: #eee;
  text-align: center;
  padding: 20px;
  font-size: 15px;
}

.site-footer a {
  color: #eee;
  text-decoration: none;
  margin: 0 8px;
}

/* Responsive */
@media (max-width: 600px) {
  .site-header {
    flex-direction: row;
    align-items: flex-start;
    justify-content: space-between;
  }

  .level-btn {
    margin-top: 0px;
    width: 180px;
  }

  .tile {
    width: 45%;
  }
}