:root {
  /* Light Theme */
  --color-bg: #FDF5E6; /* Old Lace */
  --color-surface: #FFFFFF;
  --color-text: #2B2D42;
  --color-primary: #D90429; /* Cardinal Red */
  --color-primary-hover: #EF233C;
  --color-secondary: #8D99AE;
  --color-accent: #FFD700; /* Gold */
  
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.1);
  
  --font-family-base: 'Inter', sans-serif;
  --font-family-heading: 'Noto Sans SC', sans-serif;
  
  --radius-md: 12px;
  --radius-lg: 24px;
}

body.dark-mode {
  /* Dark Theme */
  --color-bg: #1A1A1A;
  --color-surface: #2D2D2D;
  --color-text: #EDF2F4;
  --color-primary: #EF233C;
  --color-primary-hover: #D90429;
  --color-secondary: #8D99AE;
  --color-accent: #FFC300;
  
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.4);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.5);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-family-base);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  transition: background-color 0.3s ease, color 0.3s ease;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
  background-color: var(--color-surface);
  box-shadow: var(--shadow-sm);
}

header h1 {
  font-family: var(--font-family-heading);
  font-size: 1.5rem;
  color: var(--color-primary);
}

#theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--color-text);
  padding: 0.5rem;
  border-radius: 50%;
  transition: background-color 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
}

#theme-toggle:hover {
  background-color: rgba(0,0,0,0.1);
}

body.dark-mode #theme-toggle:hover {
  background-color: rgba(255,255,255,0.1);
}

/* Icon visibility logic */
.sun-icon { display: none; }
.moon-icon { display: block; }

body.dark-mode .sun-icon { display: block; }
body.dark-mode .moon-icon { display: none; }

main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 2rem;
}

footer {
  text-align: center;
  padding: 1rem;
  font-size: 0.875rem;
  color: var(--color-secondary);
}

/* Utility classes for component usage if needed */
.card {
  background-color: var(--color-surface);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  padding: 2rem;
  width: 100%;
  max-width: 400px;
  text-align: center;
}

/* Animations */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}