/* =============== Variables & Theme =============== */
:root {
    /* Dark Theme (Default) */
    --bg-color: #0F172A;
    --text-main: #FFFFFF;
    --text-muted: #94A3B8;
    --primary: #3B82F6;
    --primary-hover: #2563EB;
    --cyan: #06B6D4;
    --glass-bg: rgba(255, 255, 255, 0.03);
    --glass-border: rgba(255, 255, 255, 0.08);
    --glass-shadow: 0 4px 30px rgba(0, 0, 0, 0.5);
    --nav-bg: rgba(15, 23, 42, 0.85);
}

[data-theme="light"] {
    --bg-color: #F8FAFC;
    --text-main: #0F172A;
    --text-muted: #475569;
    --primary: #2563EB;
    --primary-hover: #1D4ED8;
    --cyan: #0891B2;
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(0, 0, 0, 0.1);
    --glass-shadow: 0 4px 30px rgba(0, 0, 0, 0.05);
    --nav-bg: rgba(248, 250, 252, 0.9);
}

/* =============== Reset & Base =============== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 80px;
}

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color 0.4s ease, color 0.4s ease;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.section {
    padding: 100px 0;
}

.section-title {
    font-size: 2.5rem;
    margin-bottom: 3rem;
    text-align: center;
    position: relative;
    display: inline-block;
    left: 50%;
    transform: translateX(-50%);
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 20%;
    width: 60%;
    height: 3px;
    background: linear-gradient(90deg, var(--primary), var(--cyan));
    border-radius: 2px;
}

/* =============== Scroll Progress =============== */
#scroll-progress {
    position: fixed;
    top: 0;
    left: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--primary), var(--cyan));
    width: 0%;
    z-index: 9999;
    transition: width 0.1s ease-out;
}

/* =============== Glassmorphism =============== */
.glass-card {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    padding: 2rem;
    box-shadow: var(--glass-shadow);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.glass-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 32px rgba(6, 182, 212, 0.15);
}

/* =============== Navigation =============== */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: transparent;
    backdrop-filter: blur(0px);
    z-index: 1000;
    transition: all 0.4s ease;
    padding: 1.5rem 0;
}

.navbar.scrolled {
    background: var(--nav-bg);
    backdrop-filter: blur(16px);
    padding: 1rem 0;
    border-bottom: 1px solid var(--glass-border);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-main);
    text-decoration: none;
}

.logo span {
    color: var(--cyan);
}

.nav-links {
    display: flex;
    gap: 1.5rem;
    align-items: center;
}

.nav-link {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    transition: color 0.3s ease;
    position: relative;
}

.nav-link:hover, .nav-link.active {
    color: var(--cyan);
}

.nav-link::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: -4px;
    left: 0;
    background: var(--cyan);
    transition: width 0.3s ease;
}

.nav-link.active::after {
    width: 100%;
}

.hamburger {
    display: none;
    background: none;
    border: none;
    color: var(--text-main);
    cursor: pointer;
    width: 30px;
    height: 30px;
}

.theme-toggle {
    background: none;
    border: none;
    color: var(--text-main);
    cursor: pointer;
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color 0.3s ease;
}
.theme-toggle:hover {
    color: var(--cyan);
}

/* =============== Buttons =============== */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    border: none;
    font-size: 1rem;
    position: relative;
    overflow: hidden;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--cyan));
    color: #fff;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3);
}

.btn-primary:hover {
    box-shadow: 0 6px 20px rgba(6, 182, 212, 0.4);
    transform: translateY(-2px);
}

.btn-secondary {
    background: var(--glass-bg);
    color: var(--text-main);
    border: 1px solid var(--glass-border);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
}

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

.btn-outline:hover {
    background: rgba(6, 182, 212, 0.1);
    transform: translateY(-2px);
}

.btn-sm {
    padding: 0.4rem 0.8rem;
    font-size: 0.85rem;
}
.w-100 { width: 100%; }

/* Ripple Effect */
.ripple {
    position: relative;
    overflow: hidden;
}
.ripple-span {
    position: absolute;
    border-radius: 50%;
    transform: scale(0);
    animation: ripple-anim 0.6s linear;
    background-color: rgba(255, 255, 255, 0.4);
}
@keyframes ripple-anim {
    to { transform: scale(4); opacity: 0; }
}

/* =============== Hero Section =============== */
.hero-section {
    position: relative;
    height: 100vh;
    display: flex;
    align-items: center;
    overflow: hidden;
}

#particle-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    opacity: 0.6;
}

.hero-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 1;
}

.hero-text {
    flex: 1;
    max-width: 600px;
}

.greeting {
    font-size: 1.2rem;
    color: var(--cyan);
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.name {
    font-size: 4rem;
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 1rem;
    background: linear-gradient(90deg, #fff, var(--text-muted));
    -webkit-background-clip: text;
    background-clip: text; /* Standard property added here */
    -webkit-text-fill-color: transparent;
}

[data-theme="light"] .name {
    background: linear-gradient(90deg, var(--text-main), var(--primary));
    -webkit-background-clip: text;
    background-clip: text; /* Standard property added here */
}

.title {
    font-size: 2rem;
    color: var(--text-muted);
    margin-bottom: 1.5rem;
    height: 40px;
}

.cursor {
    animation: blink 0.8s infinite;
    color: var(--cyan);
}
@keyframes blink {
    0%, 100% { opacity: 1; }
    50% { opacity: 0; }
}

.hero-description {
    font-size: 1.1rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.hero-image-wrapper {
    flex: 1;
    display: flex;
    justify-content: center;
}

.image-placeholder {
    width: 350px;
    height: 450px;
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, rgba(59,130,246,0.1), rgba(6,182,212,0.1));
    padding: 0;
    overflow: hidden;
}

.image-placeholder svg {
    width: 100px;
    height: 100px;
    color: var(--cyan);
    opacity: 0.5;
}

/* =============== About Section =============== */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
}

.about-text h3 {
    color: var(--cyan);
    margin-bottom: 0.5rem;
    margin-top: 1.5rem;
}
.about-text h3:first-child { margin-top: 0; }

.stats-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
}

.stat-card {
    text-align: center;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.stat-card h3 {
    font-size: 3rem;
    color: var(--primary);
    margin-bottom: 0.5rem;
}

/* =============== Skills Section =============== */
.skills-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
}

.skill-category h3 {
    margin-bottom: 1.5rem;
    color: var(--cyan);
    text-align: center;
}

.skill-item {
    margin-bottom: 1.2rem;
}

.skill-info {
    display: flex;
    justify-content: space-between;
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
    font-weight: 500;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--glass-border);
    border-radius: 4px;
    overflow: hidden;
}

.progress {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--cyan));
    border-radius: 4px;
    width: 0; /* Animated by JS */
    transition: width 1.5s cubic-bezier(0.1, 0.7, 0.1, 1);
}

/* =============== Experience & Education Timeline =============== */
.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

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

.timeline-item {
    position: relative;
    padding-left: 60px;
    margin-bottom: 2rem;
}

.timeline-dot {
    position: absolute;
    width: 16px;
    height: 16px;
    background: var(--cyan);
    border-radius: 50%;
    left: 13px;
    top: 24px;
    box-shadow: 0 0 10px var(--cyan);
}

.timeline-content {
    padding: 1.5rem;
}
.timeline-content h3 { color: var(--text-main); font-size: 1.3rem;}
.timeline-content h4 { color: var(--primary); font-size: 1rem; margin-bottom: 0.5rem;}
.timeline-date {
    display: inline-block;
    padding: 0.3rem 0.8rem;
    background: var(--glass-border);
    border-radius: 20px;
    font-size: 0.85rem;
    margin-bottom: 1rem;
    color: var(--cyan);
}

/* =============== Projects Section =============== */
.filter-container {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 3rem;
    flex-wrap: wrap;
}

.filter-btn {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    padding: 0.5rem 1.2rem;
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.filter-btn:hover, .filter-btn.active {
    background: var(--cyan);
    color: #fff;
    border-color: var(--cyan);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 2rem;
}

.project-card {
    display: flex;
    flex-direction: column;
    padding: 0;
    overflow: hidden;
}

.project-img-placeholder {
    height: 200px;
    background: rgba(0,0,0,0.2);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
    font-weight: 500;
    border-bottom: 1px solid var(--glass-border);
}

.project-content {
    padding: 1.5rem;
    flex: 1;
    display: flex;
    flex-direction: column;
}

.project-content h3 {
    margin-bottom: 0.5rem;
    font-size: 1.2rem;
}

.project-content p {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 1rem;
    flex: 1;
}

.tech-stack {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.tech-stack span {
    font-size: 0.75rem;
    padding: 0.2rem 0.6rem;
    background: rgba(59, 130, 246, 0.1);
    color: var(--cyan);
    border-radius: 4px;
    border: 1px solid rgba(6, 182, 212, 0.2);
}

.project-links {
    display: flex;
    gap: 1rem;
}

/* =============== Certifications Section =============== */
.cert-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.cert-card {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.cert-img {
    width: 80px;
    height: 80px;
    background: var(--glass-border);
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.7rem;
    text-align: center;
    padding: 0.5rem;
    color: var(--text-muted);
}

.cert-info h3 { font-size: 1.1rem; }
.cert-info p { color: var(--primary); font-size: 0.9rem; margin-bottom: 0.5rem;}
.cert-info span { display: block; color: var(--text-muted); font-size: 0.8rem; margin-bottom: 0.5rem;}

/* =============== Thesis Section =============== */
.thesis-card {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 2rem;
    align-items: center;
}

.thesis-img {
    width: 100%;
    height: 400px;
    background: var(--glass-border);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
}

.thesis-content h3 {
    font-size: 1.5rem;
    color: var(--cyan);
    margin-bottom: 1.5rem;
}

.thesis-section {
    margin-bottom: 1rem;
}
.thesis-section h4 { color: var(--text-main); font-size: 1rem;}
.thesis-section p { color: var(--text-muted); font-size: 0.95rem;}
.thesis-section ul { color: var(--text-muted); font-size: 0.95rem; }

/* =============== Resume Section =============== */
.center-text { text-align: center; }
.resume-preview {
    max-width: 600px;
    margin: 0 auto;
    padding: 3rem 2rem;
}
.resume-icon {
    width: 60px;
    height: 60px;
    margin-bottom: 1rem;
}

/* =============== Thesis Section Image 2 =============== */
.thesis-img {
    width: 100%;
    height: auto;
    background: var(--glass-border);
    border-radius: 12px;
    display: flex;
    flex-direction: column; /* ছবিগুলোকে ওপর-নিচ বরাবর সাজানোর জন্য */
    gap: 1.5rem; /* দুটি ছবির মাঝখানে ফাঁকা জায়গা */
    padding: 1.5rem; /* ভেতরের দিকে কিছুটা স্পেস রাখার জন্য */
    align-items: center;
    justify-content: center;
    overflow: hidden; /* ছবির কোণাগুলো যেন কার্ডের শেপের সাথে মিলে যায় */
}

.thesis-img img {
    width: 100%;
    height: auto;
    border-radius: 8px;
    object-fit: cover; /* ছবিটি চ্যাপ্টা না হয়ে সুন্দরভাবে ফিট হবে */
}

/* =============== Contact Section =============== */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: 3rem;
}

.contact-card {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    padding: 1.5rem;
    margin-bottom: 1rem;
}
.contact-icon { font-size: 1.5rem; }
.contact-card h4 { color: var(--text-main); }
.contact-card p { color: var(--text-muted); font-size: 0.9rem;}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    position: relative;
}

.form-group label {
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
    color: var(--text-muted);
}

.form-group input, .form-group textarea {
    width: 100%;
    padding: 0.8rem 1rem;
    background: rgba(0,0,0,0.1);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    color: var(--text-main);
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-group input:focus, .form-group textarea:focus {
    outline: none;
    border-color: var(--cyan);
    background: rgba(0,0,0,0.2);
}

.error-msg {
    color: #ef4444;
    font-size: 0.8rem;
    margin-top: 0.3rem;
    display: none;
}
.form-group.error input, .form-group.error textarea { border-color: #ef4444; }
.form-group.error .error-msg { display: block; }

.success-msg {
    color: #10b981;
    text-align: center;
    display: none;
    padding: 1rem;
    background: rgba(16, 185, 129, 0.1);
    border-radius: 8px;
}

/* =============== Footer =============== */
.footer {
    background: var(--nav-bg);
    border-top: 1px solid var(--glass-border);
    padding: 3rem 0;
    text-align: center;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    margin-bottom: 1.5rem;
}

.social-links a {
    color: var(--text-muted);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    transition: all 0.3s ease;
}

.social-links a:hover {
    color: var(--cyan);
    transform: translateY(-3px);
    border-color: var(--cyan);
}

.social-links svg { width: 20px; height: 20px; }

.footer p { color: var(--text-muted); font-size: 0.9rem;}

/* =============== Utilities & Animations =============== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 45px;
    height: 45px;
    background: linear-gradient(135deg, var(--primary), var(--cyan));
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    z-index: 999;
    box-shadow: 0 4px 15px rgba(6, 182, 212, 0.4);
}

.back-to-top.show {
    opacity: 1;
    visibility: visible;
}
.back-to-top:hover { transform: translateY(-5px); }
.back-to-top svg { width: 24px; height: 24px; }

/* Scroll Animations Setup */
.scroll-animate {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease, transform 0.8s cubic-bezier(0.1, 0.7, 0.1, 1);
}
.scroll-animate.show {
    opacity: 1;
    transform: translateY(0);
}

/* Initial Load Animations */
.animate-fade-up {
    animation: fadeUp 1s cubic-bezier(0.1, 0.7, 0.1, 1) forwards;
}
.animate-fade-in {
    opacity: 0;
    animation: fadeIn 1.5s ease 0.5s forwards;
}

@keyframes fadeUp {
    from { opacity: 0; transform: translateY(40px); }
    to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeIn {
    to { opacity: 1; }
}

/* =============== Responsive Design =============== */
@media (max-width: 992px) {
    .name { font-size: 3rem; }
    .title { font-size: 1.5rem; }
    .hero-content { flex-direction: column-reverse; text-align: center; gap: 3rem;}
    .hero-buttons { justify-content: center; }
    .thesis-card { grid-template-columns: 1fr; }
    .about-grid { grid-template-columns: 1fr; }
    .skills-grid { grid-template-columns: 1fr; }
    .contact-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
    .hamburger { display: block; z-index: 1001;}
    .nav-links {
        position: fixed;
        top: 0;
        right: -100%;
        width: 70%;
        height: 100vh;
        background: var(--bg-color);
        flex-direction: column;
        justify-content: center;
        transition: right 0.4s ease;
        border-left: 1px solid var(--glass-border);
    }
    .nav-links.active { right: 0; }
    .nav-link { font-size: 1.2rem; }
    .timeline::before { left: 15px; }
    .timeline-dot { left: 8px; }
    .timeline-item { padding-left: 45px; }
    .stats-grid { grid-template-columns: 1fr; }
}

.profile-img {
    width: 100%;
    height: 100%;
    object-fit: cover; /* ছবির অনুপাত ঠিক রেখে কার্ডের ভেতর ফিট করবে */
    border-radius: 20px; /* কার্ডের বর্ডারের সাথে মিলিয়ে ছবিটিকে গোলাকার করবে */
    transition: opacity 0.5s ease-in-out;
}

/* ছবি লুকানোর জন্য নতুন একটি ক্লাস */
.fade-out {
    opacity: 0;
}

/* =============== Certifications Section =============== */
.cert-img {
    width: 80px;
    height: 80px;
    border-radius: 8px;
    overflow: hidden; /* ছবির কোণা গোল করার জন্য */
    flex-shrink: 0; /* ছোট স্ক্রিনেও ছবির সাইজ ঠিক রাখার জন্য */
    background: var(--glass-border);
}

/* ছবির অনুপাত ঠিক রাখার জন্য */
.cert-img img {
    width: 100%;
    height: 100%;
    object-fit: cover; /* ছবিটি পারফেক্টভাবে বক্সের ভেতর ফিট হবে */
}

/* =============== Dynamic Project Images =============== */
.project-image-container {
    height: 200px;
    overflow: hidden; /* ছবির বাড়তি অংশ কেটে ফেলবে */
    border-bottom: 1px solid var(--glass-border);
    position: relative;
}

.project-img {
    width: 100%;
    height: 100%;
    object-fit: cover; /* ছবিটি না চ্যাপ্টা হয়ে সুন্দরভাবে জায়গা নিয়ে বসবে */
    transition: transform 0.4s ease; /* জুম ইফেক্টের জন্য */
}

/* মাউস নিলে ছবির উপর সুন্দর একটি জুম ইফেক্ট হবে */
.project-card:hover .project-img {
    transform: scale(1.05); 
}