:root {
  --bg: #ffffff;
  --text: #1a1a1a;
  --header-bg: #f5f5f5;
  --border: #dddddd;
  --btn-bg: #0066cc;
  --btn-text: #ffffff;
  --toggle-bg: #333333;
  --toggle-text: #ffffff;
}

[data-theme="dark"] {
  --bg: #121212;
  --text: #e0e0e0;
  --header-bg: #1e1e1e;
  --border: #333333;
  --btn-bg: #4a9eff;
  --btn-text: #000000;
  --toggle-bg: #f0c040;
  --toggle-text: #000000;
}

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

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: sans-serif;
  transition: background-color 0.3s, color 0.3s;
  min-height: 100vh;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 24px;
  background-color: var(--header-bg);
  border-bottom: 1px solid var(--border);
  transition: background-color 0.3s, border-color 0.3s;
}

main {
  padding: 40px 24px;
}

#theme-toggle {
  background-color: var(--toggle-bg);
  color: var(--toggle-text);
  border: none;
  border-radius: 20px;
  padding: 8px 16px;
  cursor: pointer;
  font-size: 14px;
  transition: background-color 0.3s, color 0.3s;
}

#theme-toggle:hover {
  opacity: 0.85;
}

button {
  background-color: var(--btn-bg);
  color: var(--btn-text);
  border: none;
  border-radius: 6px;
  padding: 10px 20px;
  cursor: pointer;
  font-size: 15px;
  transition: background-color 0.3s, opacity 0.2s;
}

button:hover {
  opacity: 0.85;
}