/* Base */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg: #ffffff;
  --text: #111111;
  --header-bg: #f5f5f5;
  --border: #dddddd;
  --btn-bg: #111111;
  --btn-text: #ffffff;
  --btn-hover: #333333;
}

[data-theme="dark"] {
  --bg: #121212;
  --text: #eeeeee;
  --header-bg: #1e1e1e;
  --border: #333333;
  --btn-bg: #eeeeee;
  --btn-text: #111111;
  --btn-hover: #cccccc;
}

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  transition: background-color 0.3s ease, color 0.3s ease;
  min-height: 100vh;
}

.container {
  max-width: 800px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.5rem;
  background-color: var(--header-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  margin-bottom: 2rem;
  transition: background-color 0.3s ease, border-color 0.3s ease;
}

header h1 {
  font-size: 1.5rem;
  font-weight: 700;
}

#theme-toggle {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  background-color: var(--btn-bg);
  color: var(--btn-text);
  border: none;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 500;
  transition: background-color 0.2s ease, transform 0.1s ease;
}

#theme-toggle:hover {
  background-color: var(--btn-hover);
  transform: scale(1.03);
}

#theme-toggle:active {
  transform: scale(0.97);
}

main {
  padding: 1.5rem;
  border: 1px solid var(--border);
  border-radius: 12px;
  transition: border-color 0.3s ease;
}

main p {
  line-height: 1.7;
  font-size: 1rem;
}