/* Reset & Box Sizing */
*, *::before, *::after {
    box-sizing: border-box;
}

/* Light / System Default Theme Variables */
:root {
    --text-color: #333333;
    --bg-color: #f9f9f9;
    --link-color: #0056b3;
    --header-bg: #ffffff;
    --card-bg: #ffffff;
    --border-color: #e0e0e0;
    --shadow: 0 2px 4px rgba(0,0,0,0.05);
}

/* Automatic Dark Mode (OS Preference) */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --text-color: #e0e0e0;
        --bg-color: #121212;
        --link-color: #66b2ff;
        --header-bg: #1e1e1e;
        --card-bg: #1e1e1e;
        --border-color: #333333;
        --shadow: 0 2px 8px rgba(0,0,0,0.4);
    }
}

/* Manual Dark Mode Override */
[data-theme="dark"] {
    --text-color: #e0e0e0;
    --bg-color: #121212;
    --link-color: #66b2ff;
    --header-bg: #1e1e1e;
    --card-bg: #1e1e1e;
    --border-color: #333333;
    --shadow: 0 2px 8px rgba(0,0,0,0.4);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.site-header {
    background: var(--header-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 30px 0;
    margin-bottom: 40px;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.header-top {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
}

.logo h1 {
    margin: 0;
    font-size: 2.5rem;
}

.logo h1 a {
    text-decoration: none;
    color: var(--text-color);
}

.logo p {
    margin: 5px 0 20px 0;
    color: var(--text-color);
    opacity: 0.7;
    font-style: italic;
}

/* Dark Mode Switch Button */
.theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-color);
    font-size: 1.2rem;
    padding: 8px 12px;
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.theme-toggle:hover {
    background: var(--border-color);
}

/* Header Banner Image */
.header-banner {
    margin: 20px 0;
    width: 100%;
    overflow: hidden;
    border-radius: 4px;
    background-color: var(--border-color);
    text-align: center;
}

#header-image {
    width: 100%;
    max-height: 300px;
    object-fit: cover;
    display: block;
    transition: opacity 0.5s ease-in-out;
}

/* Navigation */
.main-nav ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    gap: 20px;
}

.main-nav a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: bold;
    padding-bottom: 5px;
}

.main-nav a:hover, .main-nav a.active {
    color: var(--link-color);
    border-bottom: 2px solid var(--link-color);
    text-decoration: none; /* Removed hover underline */
}

/* Links (Global Hover Underline Removal) */
a {
    color: var(--link-color);
    text-decoration: none;
}

a:hover {
    text-decoration: none; /* Guaranteed no underline on hover */
    opacity: 0.85;
}

/* Main Content */
main {
    flex: 1;
    width: 100%;
}

.content {
    background: var(--card-bg);
    padding: 40px;
    border-radius: 8px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    margin-bottom: 40px;
    width: 100%;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.content h1 {
    margin-top: 0;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 10px;
}

.content p {
    margin-bottom: 20px;
}

/* Footer */
.site-footer {
    text-align: center;
    padding: 20px 0;
    color: var(--text-color);
    opacity: 0.8;
    font-size: 0.9rem;
    border-top: 1px solid var(--border-color);
    background: var(--header-bg);
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

/* Mobile Responsiveness */
@media (max-width: 600px) {
    .content {
        padding: 20px;
    }
    
    .logo h1 {
        font-size: 2rem;
    }
}