/* =========================================
   Base Variables & Themes
   ========================================= */
:root {
    /* DEFAULT DARK MODE */
    --bg-color: #0b0d11;
    --text-main: #e2e8f0;
    --text-muted: #94a3b8;
    --accent-purple: #8b5cf6;
    --accent-hover: #a78bfa;
    --card-bg: #161b22;
    --border-color: #1e293b;

    /* Theme-specific elements */
    --header-bg: rgba(11, 13, 17, 0.9);
    --nav-text: var(--text-main);
    --page-header-grad: linear-gradient(to bottom, rgba(139, 92, 246, 0.1) 0%, var(--bg-color) 100%);
}

[data-theme="light"] {
    /* BRIGHT MODE (Eye-Relaxing & Purple Identity) */
    --bg-color: #F4F5F7;
    --text-main: #2D3748;
    --text-muted: #4A5568;
    --accent-purple: #6B46C1;
    --accent-hover: #553C9A;
    --card-bg: #FFFFFF;
    --border-color: #E2E8F0;

    --header-bg: rgba(90, 50, 163, 0.98);
    --nav-text: #FFFFFF;
    --page-header-grad: linear-gradient(to bottom, rgba(107, 70, 193, 0.12) 0%, var(--bg-color) 100%);
}

/* =========================================
   Reset & Shared
   ========================================= */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Roboto', 'Segoe UI', Helvetica, Arial, sans-serif;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 90px;
}

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color 0.3s ease, color 0.3s ease;

    /* ADD THESE THREE LINES */
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Dim images to reduce glare (Disabled in Bright Mode) */
img {
    filter: brightness(0.85) contrast(1.05);
    transition: filter 0.3s ease;
}

img:hover,
.card:hover .card-img {
    filter: brightness(1) contrast(1);
}

[data-theme="light"] img {
    filter: none;
}

/* =========================================
   Navigation
   ========================================= */
header {
    padding: 1.5rem 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    background-color: var(--header-bg);
    backdrop-filter: blur(10px);
    z-index: 1000;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.logo img {
    height: 30px;
    display: block;
    filter: none !important;
    /* Keep logo clear */
    transition: all 0.3s ease;
}

nav ul {
    list-style: none;
    display: flex;
    align-items: center;
    gap: 2rem;
}

nav a {
    color: var(--nav-text);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
}

nav a:hover,
nav a.active {
    color: var(--accent-purple);
}

[data-theme="light"] nav a:hover,
[data-theme="light"] nav a.active {
    color: #D6BCFA;
}

/* Theme Toggle Button */
.theme-btn {
    background: transparent;
    border: none;
    color: var(--nav-text);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem;
    border-radius: 50%;
    transition: all 0.3s ease;
}

.theme-btn:hover {
    background-color: rgba(255, 255, 255, 0.1);
    transform: scale(1.1);
}

/* =========================================
   Articles Hub Specific Styles
   ========================================= */
.page-header {
    padding: 8rem 5% 4rem;
    text-align: center;
    background: var(--page-header-grad);
    transition: background 0.3s ease;
}

.page-header h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.page-header p {
    color: var(--text-muted);
    font-size: 1.1rem;
}

/* Filter Section */
.filter-section {
    max-width: 1200px;
    margin: 0 auto 3rem auto;
    padding: 0 5%;
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.search-input {
    flex-grow: 1;
    min-width: 250px;
}

.year-filter {
    min-width: 150px;
    width: auto;
}

input,
select {
    width: 100%;
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-main);
    padding: 0.8rem 1rem;
    border-radius: 4px;
    font-size: 1rem;
    transition: border-color 0.3s ease, outline 0.3s ease, background-color 0.3s ease;
}

input:focus,
select:focus {
    outline: none;
    border-color: var(--accent-purple);
    box-shadow: 0 0 0 3px rgba(107, 70, 193, 0.1);
}

select {
    appearance: none;
    cursor: pointer;
}

/* Articles Grid & Cards */
.articles-grid {
    max-width: 1200px;
    margin: 0 auto 5rem auto;
    padding: 0 5%;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 2rem;
}

.card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    transition: border-color 0.3s ease, transform 0.3s ease, background-color 0.3s ease, box-shadow 0.3s ease;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    position: relative;
    cursor: pointer;
}

[data-theme="light"] .card {
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.02);
}

.card:hover {
    border-color: var(--accent-purple);
    transform: translateY(-5px);
}

[data-theme="light"] .card:hover {
    box-shadow: 0 10px 15px rgba(0, 0, 0, 0.05);
}

.card-img {
    width: 100%;
    height: 200px;
    object-fit: cover;
    border-bottom: 1px solid var(--border-color);
}

.card-content {
    padding: 2.5rem;
    display: flex;
    flex-direction: column;
    flex-grow: 1;
}

.card h3 {
    font-size: 1.3rem;
    margin-bottom: 1rem;
    color: var(--text-main);
    line-height: 1.3;
}

.card p {
    color: var(--text-muted);
    margin-bottom: 1.5rem;
    flex-grow: 1;
    font-size: 0.95rem;
}

.tag {
    display: inline-block;
    background-color: rgba(139, 92, 246, 0.15);
    color: var(--accent-purple);
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: bold;
    margin-bottom: 1rem;
    width: fit-content;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

[data-theme="light"] .tag {
    background-color: rgba(107, 70, 193, 0.1);
}

.read-more {
    color: var(--accent-purple);
    text-decoration: none;
    font-weight: bold;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    transition: gap 0.3s ease;
}

.card:hover .read-more {
    gap: 0.8rem;
}

.stretched-link::after {
    content: "";
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    z-index: 1;
}

/* Scroll Top & Footer */
.scroll-top-btn {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background-color: var(--accent-purple);
    color: #ffffff;
    border: none;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease, transform 0.3s ease, background-color 0.3s ease;
    z-index: 999;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.5);
}

[data-theme="light"] .scroll-top-btn {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.scroll-top-btn.show {
    opacity: 1;
    visibility: visible;
}

.scroll-top-btn:hover {
    background-color: var(--accent-hover);
    transform: translateY(-5px);
}

footer {
    text-align: center;
    padding: 2rem;
    border-top: 1px solid var(--border-color);
    background-color: var(--card-bg);
    color: var(--text-muted);
    font-size: 0.9rem;

    /* CHANGE THIS LINE */
    margin-top: auto;

    transition: background-color 0.3s ease, border-color 0.3s ease;
}

@media (max-width: 768px) {
    nav ul {
        display: none;
    }

    .scroll-top-btn {
        bottom: 20px;
        right: 20px;
    }
}