* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #2563eb;
    --secondary-color: #1e40af;
    --accent-color: #f59e0b;
    --light-color: #f8fafc;
    --dark-color: #0f172a;
    --text-color: #1e293b;
    --text-light: #64748b;
    --bg-color: #f1f5f9;
    --card-bg: #ffffff;
    --transition: all 0.3s ease;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-hover: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius: 12px;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
    overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
    margin-bottom: 0.5em;
    line-height: 1.2;
    color: var(--dark-color);
}

p {
    margin-bottom: 1em;
}

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

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

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

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.section {
    padding: 80px 0;
}

.section-title {
    text-align: center;
    margin-bottom: 50px;
    position: relative;
}

.section-title h2 {
    font-size: 2.5rem;
    display: inline-block;
    padding-bottom: 15px;
    /* ensure visible in dark mode: override if needed */
}

.section-title h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background: var(--primary-color);
    border-radius: 2px;
}

.btn {
    display: inline-block;
    background-color: var(--primary-color);
    color: white;
    padding: 12px 28px;
    border-radius: 30px;
    font-weight: 600;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    text-align: center;
}

.btn:hover {
    background-color: var(--secondary-color);
    transform: translateY(-3px);
    box-shadow: var(--shadow-hover);
}

.btn-outline {
    background-color: transparent;
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
}

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

header {
    background-color: var(--card-bg);
    box-shadow: var(--shadow);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 0;
}

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

.nav-links {
    display: flex;
    list-style: none;
}

.nav-links li {
    margin-left: 30px;
}

.nav-links a {
    color: var(--text-color);
    font-weight: 500;
    position: relative;
    padding: 5px 0;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: var(--transition);
}

.nav-links a:hover::after {
    width: 100%;
}

.dark-mode-toggle {
    background: none;
    border: none;
    font-size: 1.2rem;
    cursor: pointer;
    margin-left: 20px;
    color: var(--text-color);
}

.hero {
    height: 100vh;
    display: flex;
    align-items: center;
    background: linear-gradient(135deg, rgba(37, 99, 235, 0.9), rgba(30, 64, 175, 0.9)), url('https://images.unsplash.com/photo-1517694712202-14dd9538aa97?ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D&auto=format&fit=crop&w=2070&q=80') center/cover no-repeat;
    color: white;
    text-align: center;
    padding-top: 80px;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 20px;
}

.hero h1 {
    font-size: 3.5rem;
    margin-bottom: 20px;
    font-weight: 700;
    letter-spacing: -0.5px;
}

.hero-subtitle {
    font-size: 1.5rem;
    margin-bottom: 30px;
    font-weight: 300;
    opacity: 0.9;
}

.hero-buttons {
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
}

.about-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 40px;
    background-color: var(--card-bg);
    padding: 40px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 50px;
}

.card {
    background-color: var(--card-bg);
    border-radius: var(--radius);
    padding: 30px;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
}

.card h3 {
    color: var(--primary-color);
    margin-bottom: 20px;
    font-size: 1.5rem;
    display: flex;
    align-items: center;
}

.card h3 i {
    margin-right: 10px;
    font-size: 1.3rem;
}

.card p {
    margin-bottom: 15px;
}

.timeline {
    position: relative;
    max-width: 1000px;
    margin: 0 auto;
}

.timeline::after {
    content: '';
    position: absolute;
    width: 4px;
    background-color: var(--primary-color);
    top: 0;
    bottom: 0;
    left: 50%;
    margin-left: -2px;
}

.timeline-item {
    padding: 10px 40px;
    position: relative;
    width: 50%;
    box-sizing: border-box;
}

.timeline-item::after {
    content: '';
    position: absolute;
    width: 20px;
    height: 20px;
    background-color: var(--card-bg);
    border: 4px solid var(--primary-color);
    border-radius: 50%;
    top: 15px;
    z-index: 1;
}

.left {
    left: 0;
}

.right {
    left: 50%;
}

.left::after {
    right: -12px;
}

.right::after {
    left: -12px;
}

.timeline-content {
    padding: 25px;
    background-color: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    position: relative;
    transition: var(--transition);
}

.timeline-content:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
}

.timeline-content h4 {
    color: var(--secondary-color);
    margin-bottom: 10px;
    font-size: 1.3rem;
}

.timeline-content .date {
    color: var(--primary-color);
    font-weight: 600;
    margin-bottom: 15px;
    display: block;
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.timeline-content ul {
    padding-left: 20px;
    margin-bottom: 0;
}

.timeline-content li {
    margin-bottom: 8px;
}

.skills-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 30px;
}

.skill-category h3 {
    margin-bottom: 20px;
    color: var(--secondary-color);
    display: flex;
    align-items: center;
}

.skill-category h3 i {
    margin-right: 10px;
    color: var(--primary-color);
}

.skill-list {
    list-style: none;
}

.skill-item {
    margin-bottom: 15px;
}

.skill-name {
    display: flex;
    justify-content: space-between;
    margin-bottom: 8px;
    font-weight: 600;
}

.skill-bar {
    height: 8px;
    background-color: #e2e8f0;
    border-radius: 4px;
    overflow: hidden;
}

.skill-progress {
    height: 100%;
    background-color: var(--primary-color);
    border-radius: 4px;
    width: 0;
    transition: width 1.5s ease-in-out;
}

.project-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
    gap: 30px;
}

.project-card {
    background-color: var(--card-bg);
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

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

.project-img {
    height: 200px;
    background-color: #cbd5e1;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-light);
    font-size: 1.2rem;
}

.project-content {
    padding: 25px;
}

.project-content h3 {
    margin-bottom: 15px;
    color: var(--secondary-color);
}

.project-content p {
    margin-bottom: 20px;
    color: var(--text-color);
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 20px;
}

.tag {
    background-color: #dbeafe;
    color: var(--primary-color);
    padding: 5px 12px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 500;
}

.contact-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 40px;
    background-color: var(--card-bg);
    padding: 40px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.contact-info {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.contact-item {
    display: flex;
    align-items: flex-start;
    gap: 15px;
}

.contact-icon {
    width: 50px;
    height: 50px;
    background-color: var(--primary-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.2rem;
    flex-shrink: 0;
}

.contact-text h4 {
    margin-bottom: 5px;
    color: var(--secondary-color);
}

.contact-form .form-group {
    margin-bottom: 20px;
}

.contact-form label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: var(--dark-color);
}

.form-control {
    width: 100%;
    padding: 12px 15px;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    font-family: inherit;
    font-size: 1rem;
    transition: var(--transition);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.2);
}

textarea.form-control {
    min-height: 150px;
    resize: vertical;
}

footer {
    background-color: var(--dark-color);
    color: white;
    text-align: center;
    padding: 40px 0;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin: 30px 0;
}

.social-links a {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: rgba(255, 255, 255, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.2rem;
    transition: var(--transition);
    text-decoration: none;
}

.social-links a:hover {
    background-color: var(--primary-color);
    transform: translateY(-5px);
}

.footer-bottom {
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 0.9rem;
    color: #94a3b8;
}

.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background-color: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    font-size: 1.2rem;
    box-shadow: var(--shadow);
    transition: var(--transition);
    z-index: 999;
    opacity: 0;
    visibility: hidden;
}

.back-to-top.show {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background-color: var(--secondary-color);
    transform: translateY(-5px);
}

.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* Dark Mode Styles */
body.dark-mode {
    background-color: #0f172a;
    color: #e2e8f0;
}

body.dark-mode .card,
body.dark-mode .about-container,
body.dark-mode .contact-container,
body.dark-mode .timeline-content {
    background-color: #1e293b;
    color: #e2e8f0;
}

body.dark-mode .skill-bar {
    background-color: #334155;
}

body.dark-mode .form-control {
    background-color: #334155;
    color: #e2e8f0;
    border-color: #475569;
}

body.dark-mode .section-title h2 {
    color: #e2e8f0;
}

body.dark-mode h1,
body.dark-mode h2,
body.dark-mode h3,
body.dark-mode h4 {
    color: #e2e8f0;
}

body.dark-mode header {
    background-color: #1e293b;
}

body.dark-mode .nav-links a {
    color: #e2e8f0;
}

body.dark-mode .dark-mode-toggle {
    color: #e2e8f0;
}

/* Responsive Media Queries */
@media (max-width: 992px) {
    .timeline::after {
        left: 31px;
    }

    .timeline-item {
        width: 100%;
        padding-left: 70px;
        padding-right: 25px;
    }

    .timeline-item::after {
        left: 21px;
    }

    .left::after, .right::after {
        left: 21px;
    }

    .right {
        left: 0%;
    }
}

@media (max-width: 768px) {
    .hero h1 {
        font-size: 2.5rem;
    }

    .hero-subtitle {
        font-size: 1.2rem;
    }

    .nav-links {
        display: none;
    }

    .mobile-menu-btn {
        display: block;
        background: none;
        border: none;
        color: var(--text-color);
        font-size: 1.5rem;
        cursor: pointer;
    }

    .project-grid,
    .skills-container,
    .cards-container {
        grid-template-columns: 1fr;
    }

    .section {
        padding: 60px 0;
    }
}

@media (max-width: 480px) {
    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }

    .btn {
        width: 100%;
        max-width: 300px;
    }
}