/* ======================= Google Fonts Import ======================= */
/* This is already in the HTML, but good practice to note it here */
/* @import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;500;600;700&family=Hind+Siliguri:wght@400;500;600&display=swap'); */

/* ======================= CSS Variables ======================= */
:root {
    --primary-color: #4a90e2; /* A professional blue */
    --secondary-color: #50e3c2; /* A vibrant accent teal */
    --background-color: #f4f7f9; /* Light grey background */
    --surface-color: #ffffff; /* Card and surface background */
    --text-color: #333333; /* Dark grey for text */
    --light-text-color: #777777; /* Lighter grey for subtitles */
    --border-color: #e0e0e0;

    --font-primary: 'Poppins', sans-serif;
    --font-secondary: 'Hind Siliguri', sans-serif; /* For Bengali content if needed */
    
    --shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
    --transition: all 0.3s ease;
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-primary);
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 2rem;
}

h1, h2, h3 {
    font-weight: 600;
}

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

a:hover {
    opacity: 0.8;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
}

section {
    padding: 6rem 0;
}

.section-title {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 1rem;
}

.section-subtitle {
    text-align: center;
    font-size: 1.1rem;
    color: var(--light-text-color);
    max-width: 600px;
    margin: 0 auto 4rem auto;
}

/* ======================= Header / Navbar ======================= */
.header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    z-index: 100;
    transition: var(--transition);
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 5rem;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.nav-logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-color);
}

.nav-menu {
    display: flex;
    gap: 2rem;
}

.nav-link {
    font-weight: 500;
    color: var(--light-text-color);
}

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

.hamburger {
    display: none;
    cursor: pointer;
}

.bar {
    display: block;
    width: 25px;
    height: 3px;
    margin: 5px auto;
    background-color: var(--text-color);
    transition: var(--transition);
}

/* ======================= Hero Section ======================= */
.hero-section {
    padding-top: 5rem; /* For fixed header */
    min-height: 100vh;
    display: flex;
    align-items: center;
}

.hero-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 2rem;
    width: 100%;
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 2rem;
}

.hero-text h1 {
    font-size: 3.5rem;
    line-height: 1.2;
}

.hero-text .tagline {
    font-size: 1.5rem;
    color: var(--primary-color);
    font-weight: 500;
    margin: 0.5rem 0 1rem;
}

.hero-text .intro {
    font-size: 1.1rem;
    color: var(--light-text-color);
    margin-bottom: 2rem;
    max-width: 500px;
}

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

.btn {
    padding: 0.8rem 1.8rem;
    border-radius: 5px;
    font-weight: 500;
    display: inline-block;
    border: 2px solid transparent;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background-color: #3a80d2;
    color: white;
}

.btn-secondary {
    background-color: transparent;
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.btn-secondary:hover {
    background-color: var(--primary-color);
    color: white;
}

.hero-image img {
    width: 350px;
    height: 350px;
    object-fit: cover;
    border-radius: 50%;
    border: 5px solid var(--surface-color);
    box-shadow: var(--shadow);
}


/* ======================= About Section ======================= */
.about-section {
    background-color: var(--surface-color);
}
.about-section p {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
    font-size: 1.1rem;
}

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

.skill-category {
    background-color: var(--surface-color);
    padding: 2rem;
    border-radius: 10px;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.skill-category:hover {
    transform: translateY(-5px);
}

.skill-category h3 {
    font-size: 1.3rem;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.8rem;
    color: var(--primary-color);
}

.skill-category ul li {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

.skill-category ul li:last-child {
    border-bottom: none;
}


/* ======================= Experience Section (Timeline) ======================= */
.experience-section {
    background-color: var(--surface-color);
}

.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 10px;
    top: 0;
    bottom: 0;
    width: 2px;
    background-color: var(--primary-color);
}

.timeline-item {
    position: relative;
    margin-bottom: 3rem;
    padding-left: 3rem;
}

.timeline-dot {
    position: absolute;
    left: 0;
    top: 5px;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background-color: var(--surface-color);
    border: 3px solid var(--primary-color);
}

.timeline-content h3 {
    font-size: 1.4rem;
    margin-bottom: 0.2rem;
}

.timeline-content .company {
    font-weight: 500;
    color: var(--light-text-color);
}

.timeline-content .date {
    font-size: 0.9rem;
    color: var(--primary-color);
    margin-bottom: 0.8rem;
}

.timeline-content ul {
    list-style-type: disc;
    padding-left: 1.2rem;
}

/* ======================= Projects Section ======================= */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2rem;
}

.project-card {
    background-color: var(--surface-color);
    border-radius: 10px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
}

.project-card:hover {
    transform: translateY(-10px);
}

.project-card img {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

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

.project-info h3 {
    margin-bottom: 0.5rem;
}

.project-info p {
    font-size: 0.95rem;
    color: var(--light-text-color);
    flex-grow: 1;
    margin-bottom: 1rem;
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.project-tags span {
    background-color: #eef5ff;
    color: var(--primary-color);
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
}

.project-links a {
    font-size: 1.5rem;
    margin-right: 1rem;
    color: var(--light-text-color);
}

.project-links a:hover {
    color: var(--primary-color);
}

/* ======================= Contact Section ======================= */
.contact-section {
    text-align: center;
}

.email-link {
    font-size: 1.5rem;
    font-weight: 500;
    display: inline-block;
    margin: 1rem 0 2rem;
}

.social-links a {
    font-size: 2rem;
    margin: 0 1rem;
    color: var(--text-color);
}

.social-links a:hover {
    color: var(--primary-color);
    transform: scale(1.1);
}

/* ======================= Footer ======================= */
.footer {
    background-color: var(--text-color);
    color: #e0e0e0;
    text-align: center;
    padding: 2rem 0;
}

/* ======================= Responsive Design (Media Queries) ======================= */

/* For Tablets and smaller devices */
@media (max-width: 992px) {
    .section-title {
        font-size: 2rem;
    }
    
    .hero-text h1 {
        font-size: 3rem;
    }

    .hero-image img {
        width: 300px;
        height: 300px;
    }
}

/* For Mobile devices */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 5rem;
        flex-direction: column;
        background-color: var(--surface-color);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: 0 10px 20px rgba(0,0,0,0.1);
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-item {
        padding: 1.5rem 0;
    }

    .hamburger {
        display: block;
    }

    .hamburger.active .bar:nth-child(2) {
        opacity: 0;
    }

    .hamburger.active .bar:nth-child(1) {
        transform: translateY(8px) rotate(45deg);
    }

    .hamburger.active .bar:nth-child(3) {
        transform: translateY(-8px) rotate(-45deg);
    }
    
    .hero-content {
        flex-direction: column-reverse;
        text-align: center;
    }

    .hero-text {
        margin-top: 2rem;
    }

    .hero-buttons {
        justify-content: center;
    }

    .timeline::before {
        left: 50%;
        transform: translateX(-50%);
    }

    .timeline-item {
        width: 100%;
        padding-left: 0;
        padding-right: 0;
        text-align: center;
    }
    
    .timeline-dot {
        left: 50%;
        transform: translateX(-50%);
    }

    .timeline-content {
        margin-top: 3rem;
    }
}