:root {
  --background-color: #f0f2f5;
  --text-color: #333;
  --container-background: white;
}

body.dark-mode {
  --background-color: #121212;
  --text-color: #e0e0e0;
  --container-background: #1e1e1e;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  background-image: url('https://raw.githubusercontent.com/hiroshi-matsuda-jp/seigaiha-pattern/main/seigaiha-pattern-medium.png');
  background-repeat: repeat;
  background-size: 200px; /* Adjust size as needed */
  background-color: var(--background-color); /* Fallback color for themes, or blend with pattern */
  color: var(--text-color);
  transition: background-color 0.3s, color 0.3s;
}

#theme-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
    padding: 10px;
    border: none;
    background-color: #4CAF50;
    color: white;
    border-radius: 5px;
    cursor: pointer;
}

.container {
  text-align: center;
  padding: 2rem;
  background-color: var(--container-background);
  border-radius: 10px;
  box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}

h1 {
  font-size: 2.5rem;
  color: var(--text-color);
  margin-bottom: 2rem;
}