/* ==============================
   CSS Variables & Design Tokens (HARRYoo7 Theme)
============================== */
:root {
    --bg-color: #0a192f;
    --bg-color-light: #112240;
    --text-primary: #ccd6f6;
    --text-secondary: #8892b0;
    --accent: #64ffda;
    --accent-tint: rgba(100, 255, 218, 0.1);
    
    --font-sans: 'Inter', -apple-system, sans-serif;
    --font-heading: 'Space Grotesk', sans-serif;
    --font-mono: 'Fira Code', monospace;
    
    --nav-height: 80px;
    --transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
}

/* ==============================
   Global Reset & Typography
============================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scrollbar-width: thin;
    scrollbar-color: var(--text-secondary) var(--bg-color);
}

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-sans);
    line-height: 1.6;
    overflow-x: hidden;
}

h1, h2, h3, h4, .logo {
    font-family: var(--font-heading);
}

a {
    color: var(--accent);
    text-decoration: none;
    transition: var(--transition);
}

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

ul {
    list-style: none;
}

.section-padding {
    padding: 100px 0;
    max-width: 1000px;
    margin: 0 auto;
    width: 90%;
}

.section-title {
    font-size: 2rem;
    color: var(--text-primary);
    margin-bottom: 40px;
    display: flex;
    align-items: center;
}

.section-title::after {
    content: "";
    display: block;
    height: 1px;
    width: 300px;
    background-color: var(--bg-color-light);
    margin-left: 20px;
    flex-grow: 1;
}

.accent {
    color: var(--accent);
}

/* ==============================
   Glassmorphism Utility
============================== */
.glass-card {
    background: rgba(17, 34, 64, 0.5);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: 12px;
    padding: 30px;
    transition: var(--transition);
}

.glass-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px -15px rgba(2, 12, 27, 0.7);
    border-color: var(--accent-tint);
}

/* ==============================
   Buttons
============================== */
.btn {
    display: inline-block;
    padding: 0.85rem 1.5rem;
    border-radius: 4px;
    font-family: var(--font-heading);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    border: none;
    text-decoration: none;
}

.btn-primary {
    background-color: var(--accent);
    color: var(--bg-color);
    font-weight: 700;
}

.btn-primary:hover {
    background-color: transparent;
    color: var(--accent);
    border: 1px solid var(--accent);
}

.btn-outline {
    background-color: transparent;
    color: var(--accent);
    border: 1px solid var(--accent);
}

.btn-outline:hover {
    background-color: var(--accent-tint);
}

/* ==============================
   Navigation
============================== */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    height: var(--nav-height);
    background: rgba(10, 25, 47, 0.85);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    z-index: 100;
    transition: var(--transition);
}

.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 30px;
    height: 100%;
}

.logo {
    font-size: 2rem;
    font-weight: 700;
    color: var(--accent);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 25px;
}

.nav-links a {
    color: var(--text-primary);
    font-size: 0.9rem;
}

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

.nav-links a.external-link {
    color: var(--accent);
    background: var(--accent-tint);
    padding: 6px 12px;
    border-radius: 4px;
    border: 1px solid rgba(100, 255, 218, 0.2);
}

/* ==============================
   Hero Section
============================== */
.hero {
    min-height: 90vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    position: relative;
    padding-top: calc(var(--nav-height) + 20px);
}

.greeting {
    color: var(--accent);
    font-family: var(--font-heading);
    font-size: 1.1rem;
    margin-bottom: 20px;
}

.name {
    font-size: clamp(40px, 8vw, 72px);
    font-weight: 800;
    line-height: 1.1;
    color: var(--text-primary);
}

.role {
    font-size: clamp(26px, 5vw, 48px);
    font-weight: 700;
    color: var(--text-secondary);
    line-height: 1.1;
    margin-bottom: 25px;
}

.bio {
    color: var(--text-secondary);
    max-width: 650px;
    font-size: 1.05rem;
    line-height: 1.7;
    margin-bottom: 35px;
}

.social-links {
    display: flex;
    gap: 15px;
    flex-wrap: wrap;
}

.hero-visual {
    position: absolute;
    right: 5%;
    top: 50%;
    transform: translateY(-50%);
    z-index: -1;
    opacity: 0.5;
}

.glow-sphere {
    width: 350px;
    height: 350px;
    border-radius: 50%;
    background: radial-gradient(circle, var(--accent-tint) 0%, transparent 70%);
    filter: blur(40px);
    animation: pulse 4s ease-in-out infinite alternate;
}

@keyframes pulse {
    0% { transform: scale(0.8); opacity: 0.4; }
    100% { transform: scale(1.2); opacity: 0.8; }
}

/* ==============================
   Experience Timeline
============================== */
.timeline {
    position: relative;
    max-width: 850px;
    margin: 0 auto;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 20px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--bg-color-light);
}

.timeline-item {
    margin-bottom: 35px;
    position: relative;
    padding-left: 60px;
}

.timeline-item::before {
    content: '';
    position: absolute;
    left: 14px;
    top: 30px;
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: var(--bg-color);
    border: 2px solid var(--accent);
}

.timeline-date {
    font-family: var(--font-heading);
    font-size: 0.9rem;
    color: var(--accent);
    margin-bottom: 10px;
}

.timeline-content h3 {
    color: var(--text-primary);
    font-size: 1.3rem;
}

.timeline-content h4 {
    color: var(--text-secondary);
    font-size: 1rem;
    margin-bottom: 12px;
}

.timeline-content ul.bullets {
    list-style: disc;
    margin-left: 20px;
    color: var(--text-secondary);
    font-size: 0.93rem;
    margin-bottom: 15px;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.tech-stack {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 15px;
}

.tech-stack li {
    font-size: 0.78rem;
    font-family: var(--font-heading);
    color: var(--accent);
    background: var(--accent-tint);
    padding: 4px 10px;
    border-radius: 20px;
}

/* ==============================
   Projects Grid
============================== */
.project-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.project-card {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.project-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.project-title {
    font-size: 1.3rem;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.project-subtitle {
    font-size: 0.85rem;
    color: var(--accent);
    margin-bottom: 12px;
    font-family: var(--font-heading);
}

.project-description {
    color: var(--text-secondary);
    font-size: 0.92rem;
    margin-bottom: 20px;
    flex-grow: 1;
    line-height: 1.6;
}

/* ==============================
   Library Section
============================== */
.tabs {
    display: flex;
    gap: 20px;
    margin-bottom: 30px;
    border-bottom: 1px solid var(--bg-color-light);
    padding-bottom: 10px;
}

.tab-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-family: var(--font-heading);
    font-size: 1.05rem;
    cursor: pointer;
    position: relative;
    padding: 8px 0;
    transition: var(--transition);
}

.tab-btn:hover, .tab-btn.active {
    color: var(--accent);
}

.tab-btn.active::after {
    content: '';
    position: absolute;
    bottom: -11px;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--accent);
}

.tab-pane {
    display: none;
    animation: fadeIn 0.4s ease;
}

.tab-pane.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.reading-highlight {
    margin-bottom: 25px;
    border: 1px solid var(--accent);
    position: relative;
    overflow: hidden;
}

.reading-highlight::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background-color: var(--accent);
}

.badge {
    display: inline-block;
    background: var(--accent-tint);
    color: var(--accent);
    padding: 4px 10px;
    border-radius: 4px;
    font-size: 0.78rem;
    font-family: var(--font-heading);
    margin-bottom: 12px;
    border: 1px solid rgba(100, 255, 218, 0.2);
}

.library-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 20px;
}

.book-card h4 {
    color: var(--text-primary);
    margin-bottom: 5px;
}

.book-card p {
    color: var(--text-secondary);
    font-size: 0.88rem;
}

/* ==============================
   Footer
============================== */
footer {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-secondary);
    font-family: var(--font-heading);
    font-size: 0.9rem;
    border-top: 1px solid var(--bg-color-light);
}

/* ==============================
   Animations & Responsive
============================== */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

@media (max-width: 768px) {
    .nav-links { display: none; }
    .hero-visual { display: none; }
    .timeline::before { left: 0; }
    .timeline-item { padding-left: 30px; }
    .timeline-item::before { left: -6px; }
    .section-title::after { width: 100px; }
}