:root {
    --primary-color: #0a66c2; /* A professional blue, similar to LinkedIn's */
    --background-color: #f3f2ef;
    --card-background-color: #ffffff;
    --text-color: #333333;
    --text-color-light: #666666;
    --border-color: #e0e0e0;
    --header-footer-bg: #ffffff;
    --shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

body.dark-mode {
    --primary-color: #70b5f9;
    --background-color: #1d2226;
    --card-background-color: #2b3940;
    --text-color: #e1e9ee;
    --text-color-light: #b0b9bf;
    --border-color: #444;
    --header-footer-bg: #2b3940;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

/* --- Layout & Container --- */
.container {
    max-width: 960px;
    margin: 0 auto;
    padding: 0 20px;
}

/* --- Header & Navigation --- */
header {
    background-color: var(--header-footer-bg);
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
}

header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

header h1 {
    margin: 0;
    font-size: 1.5rem;
    color: var(--primary-color);
}

header nav {
    display: flex;
    align-items: center;
}

header nav ul {
    margin: 0;
    padding: 0;
    list-style: none;
    display: flex;
}

header nav ul li {
    margin-left: 20px;
}

header nav a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: color 0.2s;
}

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

/* --- Main Content & Cards --- */
main.container {
    padding-top: 2rem;
    padding-bottom: 2rem;
}

.card {
    background-color: var(--card-background-color);
    border-radius: 8px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow);
    transition: background-color 0.3s;
}

.card h2 {
    margin-top: 0;
    color: var(--primary-color);
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 0.5rem;
    margin-bottom: 1rem;
}

/* --- Links & Footer --- */
a {
    color: var(--primary-color);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

footer {
    text-align: center;
    padding: 2rem 0;
    background-color: var(--header-footer-bg);
    border-top: 1px solid var(--border-color);
    color: var(--text-color-light);
}

footer nav ul {
    padding: 0;
    list-style: none;
    display: inline-flex;
    gap: 15px;
}

/* --- Theme Toggle Slider --- */
.switch {
    margin-left: 20px;
    position: relative;
    top: 2px;
}
    
.theme-switch {
  display: inline-block;
  height: 28px;
  position: relative;
  width: 50px;
}

.theme-switch input {
  display:none;
}

.slider {
  background-color: var(--border-color);
  bottom: 0;
  cursor: pointer;
  left: 0;
  position: absolute;
  right: 0;
  top: 0;
  transition: .4s;
}

.slider:before {
  background-color: var(--card-background-color);
  bottom: 4px;
  content: "";
  height: 20px;
  left: 4px;
  position: absolute;
  transition: .4s;
  width: 20px;
}

input:checked + .slider {
  background-color: var(--primary-color);
}

input:checked + .slider:before {
  transform: translateX(22px);
}

.slider.round {
  border-radius: 28px;
}

.slider.round:before {
  border-radius: 50%;
}

/* --- Responsive Design --- */
@media (max-width: 768px) {
    header .container {
        flex-direction: column;
    }

    header nav {
        margin-top: 1rem;
    }
}