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

:root {
  --bg-color: #f9f9f9;
  --text-color: #222;
  --header-bg: #ffffff;
  --nav-link: #333;
  --nav-hover: #007acc;
  --border-color: #e0e0e0;
  --hr-color: #ddd;
  --footer-text: #777;
}

body.dark {
  --bg-color: #121212;
  --text-color: #eeeeee;
  --header-bg: #1c1c1c;
  --nav-link: #cccccc;
  --nav-hover: #4dabf7;
  --border-color: #333;
  --hr-color: #333;
  --footer-text: #888;
}

body {
  font-family: system-ui, sans-serif;
  line-height: 1.6;
  background-color: var(--bg-color);
  color: var(--text-color);
  scroll-behavior: smooth;
}

header {
  background: var(--header-bg);
  padding: 1rem 2rem;
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 1000;
}

#toggle-theme {
  background: none;
  font-size: 1.2rem;
  cursor: pointer;
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

nav a {
  text-decoration: none;
  color: var(--nav-link);
  font-weight: bold;
  padding-left: 1rem;
}

nav a:hover {
  color: var(--nav-hover);
}

section {
  padding: 1rem 2rem;
  max-width: 800px;
  margin: auto;
}

hr {
  border: none;
  height: 1px;
  background-color: var(--hr-color);
  margin: 2rem auto;
  max-width: 600px;
}

h1 {
  text-align: center;
  margin-bottom: 1rem;
}

#personal_title {
  text-align: center;
}

h2 {
  margin-bottom: 1rem;
}

.project {
  margin-bottom: 2rem;
}

a {
  color: var(--nav-link);
  text-decoration: none;
}

a:hover {
  color: var(--nav-hover);
  text-decoration: underline;
}

a:visited {
  color: var(--nav-link);
}

footer {
  text-align: center;
  padding: 2rem;
  font-size: 0.9rem;
  color: var(--footer-text);
}